Surfing Hangliders

Monday May 31, 2010

This is such a cool project that I had to include it in our Flying Machines archive. The science teacher who developed this project has a sincere love of gliders he calls "walk-along flyers". Note that the instructions for making this project are longer and more precise than usual, so take your time and go slow.

If your kids love airplanes, you'll be able to keep them busy for hours with this project! You will be flying a piece of paper, surfing it on a wave of air created with cardboard. Are you ready?  There are two different designs to choose from: the Tumblewing, which works by rotation, and the Hanglider.

Here's what you need:

  • piece of paper from a phone book
  • scrap of cardboard
  • scissors
  • help from a very patient adult
  • an afternoon (this project is super-sensitive and you need time and persistence to accomplish it!)

Tumblewing Design

You'll need to print out this Tumblewing template to get started.

Hanglider Design:

You'll need to print out this Hanglider template to get started.


A big THANKS goes out to projects developer and science teacher Slater Harrison for his ultra-cool flying inventions!


Stunt Flyer

Monday May 31, 2010

The best, all purpose, lazy afternoon loop-and-corkscrew stunt flying machine that we've found. This plane can easily go straight, or curve in a loop, or do a barrel roll, or boomerang back to you...and it can even do the bat maneuver (nose-up-nose-down-nose-up-nose-down-nose-up-nose-down...) with the right kind of tweaking. Spend extra time on those back elevators and you'll get a plane worthy of warm drafts.
[am4show have='p8;p9;p93;' guest_error='Guest error message' user_error='User error message' ]

 

Trouble flying? Click here to learn how to tweak your wings.

Want to know more about airplane design? Check out Why Airplanes Need Wings.

[/am4show]


Genie in a Bottle

Monday May 31, 2010

While this isn’t actually an air-pressure experiment but more of an activity in density, really, it’s still a great visual demonstration of why Hot Air Balloons rise on cold mornings.


Imagine a glass of hot water and a glass of cold water sitting on a table, side by side. Now imagine you have a way to count the number of water molecules in each glass. Which glass has more water molecules?


The glass of cold water has way more molecules… but why? The cold water is more dense than the hot water. Warmer stuff tends to rise because it’s less dense than colder stuff and that’s why the hot air balloon in experiment 1.10 floated up to the sky.


Clouds form as warm air carrying moisture rises within cooler air. As the warm, wet air rises, it cools and begins to condense, releasing energy that keeps the air warmer than its surroundings. Therefore, it continues to rise. Sometimes, in places like Florida, this process continues long enough for thunderclouds to form. Let’s do an experiment to better visualize this idea.


[am4show have=’p8;p9;p82;p84;p93;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Materials: Two identical tall glasses, hot water, cold water, red and blue food dye, and an index card larger enough to cover the opening of the glasses



Fill two identical water glasses to the brim: one with hot water, the other with cold water. Put a few drops of blue dye in the cold water, a few drops of red dye in the hot water. Place the index card over the mouth of the cold water and invert the glass over the glass of hot water. Line up the openings of both glasses, and slowly remove the card.


Troubleshooting: Always invert the cold glass over the hot glass using an index card to hold the cold water in until you’ve aligned both glasses. You can also substitute soda bottles for water glasses and slide a washer between the two bottles to decrease the flow rate between the bottles so the effect lasts longer.


[/am4show]


Soda Can Trick

Monday May 31, 2010

When air moves, the air pressure decreases. This creates a lower air pressure pocket right between the cans relative to the surrounding air. Because higher pressure pushes, the cans clink together. Just remember – whenever there’s a difference in pressure, the higher pressure pushes.


You will need about 25 straws and two empty soda cans or other lightweight containers


[am4show have=’p8;p9;p82;p84;p93;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Lay a row of straws parallel to each other on a smooth tabletop. Place two empty soda cans on the straws about an inch apart. Lower your nose to the cans and blow hard through the space between the two cans.


Clink! They should roll toward each other and touch!


[/am4show]


Rotor Kite

Monday May 31, 2010

Rotor kites (often called UFO kites) are one of those unusual kites that require more complex aerodynamics in order to fly. This particular kite flies only when rotating. Make sure you have lots of wind for this kite by either visiting the beach or tying it to your bicycle.

This kite is very picky about wind speed. Make sure the string doesn’t rub on the plates during flight. You can use hollow gardening stakes, empty ballpoint pen tubes taped together into a long straw, or composite tubes instead of the straws described here. Fishing line or nylon string works for kite line as well.

Materials: Two straws, a long length of string (20 feet or more), duct tape, two foam plates (at least 4 inches in diameter, one 6x4-inch clean foam meat tray, hot glue gun, and scissors.

Here's what you do:

[am4show have='p8;p9;p94;' guest_error='Guest error message' user_error='User error message' ]

Cut the curved sides off the short ends and cut the tray lengthwise to make two vanes. Measure the length of your vanes and add three inches to the measurement—this is the straw length you need. Tip: You can tape together several smaller straws to make one long straw.

Important: Puzzle-fit your meat tray back into its original shape. Note that there’s a lip that runs all the way around the tray. Take ONE vane and flip it over, still keeping the cut sides together. Now your rotor should have one lip facing up, the other facing down. Slide your extended straw between the cut sides of the vane and hot glue it into place.

Tip: Use duct tape to hold it together securely.

Poke a hole in the center of two foam plates. Slide one foam plate onto the straw and hot glue it in place next to the vane. Do the same for both sides.

Thread a line through the straw and tie it back onto itself, leaving enough room for the rotor to spin freely in the wind. Attach the main kite line and go find a place with lot of wind, like at the beach! Running around isn’t enough to get this kite in the air!

Tip: To see this kite working in a close-up range, get an indoor fan and set it on high speed while you hold your kite string close to the knot in the bridle. Hold your kite in the airstream until it rotates freely. Depending on where you live, you can drive your car on a country road or ride your bike to generate more wind speed than just running.

[/am4show]

Rotor kites (often called UFO kites) are one of those unusual kites that require more complex aerodynamics in order to fly. This particular kite flies only when rotating. Make sure you have lots of wind for this kite by either visiting the beach or tying it to your bicycle.

This kite is very picky about wind speed. Make sure the string doesn’t rub on the plates during flight. You can use hollow gardening stakes, empty ballpoint pen tubes taped together into a long straw, or composite tubes instead of the straws described here. Fishing line or nylon string works for kite line as well.

Materials: Two straws, a long length of string (20 feet or more), duct tape, two foam plates (at least 4 inches in diameter, one 6x4-inch clean foam meat tray, hot glue gun, and scissors.

Here's what you do:

[am4show have='p8;p9;p94;' guest_error='Guest error message' user_error='User error message' ]

Cut the curved sides off the short ends and cut the tray lengthwise to make two vanes. Measure the length of your vanes and add three inches to the measurement—this is the straw length you need. Tip: You can tape together several smaller straws to make one long straw.

Important: Puzzle-fit your meat tray back into its original shape. Note that there’s a lip that runs all the way around the tray. Take ONE vane and flip it over, still keeping the cut sides together. Now your rotor should have one lip facing up, the other facing down. Slide your extended straw between the cut sides of the vane and hot glue it into place.

Tip: Use duct tape to hold it together securely.

Poke a hole in the center of two foam plates. Slide one foam plate onto the straw and hot glue it in place next to the vane. Do the same for both sides.

Thread a line through the straw and tie it back onto itself, leaving enough room for the rotor to spin freely in the wind. Attach the main kite line and go find a place with lot of wind, like at the beach! Running around isn’t enough to get this kite in the air!

Tip: To see this kite working in a close-up range, get an indoor fan and set it on high speed while you hold your kite string close to the knot in the bridle. Hold your kite in the airstream until it rotates freely. Depending on where you live, you can drive your car on a country road or ride your bike to generate more wind speed than just running.

[/am4show]


Air Takes Space

Monday May 31, 2010

You’re about to play with one of the first methods of underwater breathing developed for scuba divers hundreds of years ago.! Back then, scientists would invert a very large clear, bell-shaped jar over a diver standing on a platform, then lower the whole thing into the water. Everyone thought this was a great idea, until the diver ran out of breathable air…


Materials: 12″ flexible tubing, two clear plastic cups, bathtub


[am4show have=’p8;p9;p93;p30;p57;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Part I: Fill the tub and climb in. Plunge one cup underwater so it fills completely with water. While the cup is underwater, point its mouth downward. Insert one end of the tubing into the cup and blow hard into the other end. The water is forced out of the cup!


Part II: While still in the tub, invert one cup (mouth downwards) and plunge it into the tub so that air gets trapped inside the cup. Place the second cup in the water so it fills with water. Invert the water-filled cup while underwater and position it above the first cup so when you tilt the first cup to release the air bubbles, they get trapped inside the second cup. Here you see that air takes space, because in both variations of this experiment the air forced the water out of the cups.


[/am4show]


Game Plan for Bubblology

Sunday May 30, 2010
Magician Tom Noody

Click here for a printer-friendly version of this page.


Objective If you’re fascinated by the simple complexity of the standard soap bubble, then this is the lab for you.  You can easily transform these ideas into a block-party Bubble Festival, or just have extra fun in the nightly bathtub.  Either way, your kids will not only learn about the science of water, molecules, and surface tension, they’ll also leave this lab cleaner than they started (which is highly unusually for science experiments!)


About the Experiments The absolute best time to make gigantic bubbles is on an overcast day, right after it rains.  Bubbles have a thin cell wall that evaporates quickly in direct sun, especially on a low-humidity day.  If you live in a dry area with low-humidity, be sure to use glycerin. The glycerin will add moisture and deter the rapid thinning of the bubble’s cell wall (which cause bubbles to tear and pop).


The How and Why Explanation If you pour a few droplets of water onto a sweater or fabric, you’ll notice that the water will just sit there on the surface in a ball (or oval, if the drop is large enough).  If you touch the ball of water with a soapy finger, the ball disappears into the fibers of the fabric!  What happened?


Soap makes water “wetter” by breaking down the water’s surface tension by about two-thirds.  Surface tension is the force that keeps the water droplet in a sphere shape.  It’s the reason you can fill a cup of water past the brim without it spilling over. Without soap, water can’t get into the fibers of your clothes to get them clean. That’s why you need soap in the washing machine.


Soap also makes water stretchy. If you’ve ever tried making bubbles with your mouth just using spit, you know that you can’t get the larger, fist-sized spit bubbles to form completely and detach to float away in the air. Spit is 94% water, and water by itself has too much surface tension, too many forces holding the molecules together.  When you add soap to it, they relax a bit and stretch out.  Soap makes water stretch and form into a bubble.


The soap molecule looks a lot like a snake; it’s a long chain that has two very different ends.  The head of the snake loves water, and the tail loves dirt.  When the soap molecule finds a dirt particle, it wraps its tail around the dirt and holds it.


The different colors of a soap bubble come from how the white light bounces off the bubble into your eye. Some of the light bounces off the top surface of the bubble and bends only a little bit, while the rest passes through the thin film and bounces off the inner surface of the bubble and refracts more.


If you made the Hover Bubbles, you’ll notice that the bubbles slowly get larger the longer they live in the tank.  Remember that the bubble is surrounded by CO2 gas as it sinks. The bubble grows because carbon dioxide seeps through the bubble film faster than the air seeps out, as CO2 is more soluble in water than air (meaning that CO2 mixes more easily with water than air does).


Questions to Ask


  1. Which soap solution makes the biggest bubbles?
  2. Does water temperature matter?
  3. How would you make a square bubble?
  4. Why can you poke a straw through a bubble after it’s been dipped in bubble solution?

Puff Rocket

Saturday May 29, 2010
Here are a few ideas for making a mini-stomp rocket called a PUFF ROCKET that uses something other than your lungs to get your rocket launched. When you do this experiment, think about which kind of bottles will work the best. And does straw length matter? In our testing, we had one rocket that cleared 25 feet!
  • clean lotion bottle or shampoo bottle
  • larger straw that fits onto a smaller straw
  • small piece of foam that fits snugly into the straws
  • hot glue gun
Here's what you do: [am4show have='p8;p9;p10;p37;p95;' guest_error='Guest error message' user_error='User error message' ]

1. Grab a clean, empty shampoo or lotion bottle. Make sure the bottle you choose gives you a good puff of air out the top cap when you squeeze it. You’ll also need two straws, one slightly smaller than the other. And a small piece of foam. 2. Insert the smaller straw into the hole in the cap. If you have trouble, ream out the hole or just take off the cap and seal the connection with a lump of clay or a lot of hot glue. Insert a small bit of foam into one end of the larger straw. Slide the larger straw (your rocket) onto the smaller straw (your launcher). 3. Squeeze the bottle hard! POOF! [/am4show]

Clothespin Catapult

Saturday May 29, 2010
This catapult requires a little more time, materials, and effort than the Fast Catapult, but it's totally worth it. This device is what most folks think of when you say 'catapult'. I've shown you how to make a small model - how large can you make yours?

This project builds on the ideas from Unit 5: Lesson 2: Kinetic Energy.

Materials:

  • plastic spoon

  • 14 popsicle sticks

  • 3 rubber bands

  • wooden clothespin

  • straw

  • wood skewer or dowel

  • scissors

  • hot glue gun


[am4show have='p8;p9;p100;' guest_error='Guest error message' user_error='User error message' ]


Try different ball weights (ping pong, foil crumpled into a ball, whiffle balls, marshmallows, etc) and chart out the results: make a data table that shows what ball you tried and how far it went. You can also use a stopwatch to time how long your ball was in the air.

You can also graph your results: make a chart where you plot each data point on a graph that has distance on the vertical axis and time on the horizontal axis.

[/am4show]

Mousetrap Car

Monday May 10, 2010
A super-fast, super-cool car that uses the pent-up energy inside a mouse trap spring to propel a homemade car forward. While normally this is reserved for high school physics classes, it really is a fun and inexpensive experiment to do with kids of all ages.

This is a great demonstration of how energy changes form. At first, the energy was  stored in the spring of the mousetrap as elastic potential energy, but after the trap is triggered, the energy is transformed into kinetic energy as rotation of the wheels.

Remember with the First Law of Thermodynamics: energy can’t be created or destroyed, but it CAN change forms. And in this case, it goes from elastic potential energy to kinetic energy.

There’s enough variation in design to really see the difference in the performance of your vehicle. If you change the size of the wheels for example, you’ll really see a difference in how far it travels. If you change the size of the wheel axle, your speed is going to change. If you alter the size of the lever arm, both your speed and distance will change. It's fun to play with the different variables to find the best vehicle you can build with your materials!

Here's what you need to do this project:

[am4show have='p8;p9;p100;' guest_error='Guest error message' user_error='User error message' ]
Materials:

  • Mousetrap (NOT a rat trap)

  • Foam block or piece of cardboard

  • Four old CDs

  • Thin string or fishing line

  • Wood dowel or long, straight piece from a wire coat hanger (use pliers to straighten it)

  • Straw

  • Two wood skewers (that fit inside straw)

  • Hot glue gun

  • Duct tape

  • Scissors

  • Four caps to water bottles

  • Drill

  • Razor with adult help




Since the directions for this project are complex, it’s really best to watch the instructions on the video. Here are the highlights:

1. Tape the dowel to the outside of the wire on the mousetrap car (see image below). When the mousetrap spans closed, the dowel whips through the air along with it in an arc.

2. Attach a length of fishing line to the other end of the dowel. Don’t cut the fishing line yet.

3. Attach one straw near each end of a block of foam using hot glue.

4. Insert a skewer into each straw. Insert a wheel onto each end of the skewer. This is your wheel-axel assembly.

5. The wheels on one side should be close to the straw, the wheels on the other end should have a 1/2” gap.

6. Thread the end of the fishing line around the wheels with the gap as shown in the video.

7. Load the mousetrap car by spinning the back wheels as you set the trap.

8. Trigger the mousetrap with a pen (never use your fingers!). The dowel pulls the fishing line, unrolling it from the axel and spinning the wheels as it opens.

What’s Going On?


Energy has a number of different forms; kinetic, potential, thermal, chemical, electrical, electrochemical, electromagnetic, sound and nuclear. All of which measure the ability of an object or system to do work on another object or system.

In the physics books, energy is the ability to do work. Work is the exertion of force over a distance. A force is a push or a pull.

So, work is when something gets pushed or pulled over a distance against a force. Mathematically:

Work = Force x Distance or W = F d

Let me give you a few examples: If I was to lift an apple up a flight of stairs, I would be doing work. I would be moving the apple against the force of gravity over a distance. However, if I were to push against a wall with all my might, and if the wall never moved, I would be doing no work because the wall never moved. (There was a force, but no distance.)

Another way to look at this, is to say that work is done if energy is changed. By pushing on the non-moving wall, no energy is changed in the wall. If I lift the apple up a flight of stairs however, the apple now has more potential energy then it had when it started. The apple’s energy has changed, so work has been done.

All the different forms of energy can be broken down into two categories: potential and kinetic energy.

My students have nicknamed potential energy the “could” energy. The battery “could” power the flashlight. The light “could” turn on. I “could” make a sound. That ball “could” fall off the wall. That candy bar “could” give me energy.

Potential energy is the energy that something has that can be released. For example, the battery has the potential energy to light the bulb of the flashlight if the flashlight is turned on and the energy is released from the battery. Your legs have the potential energy to make you hop up and down if you want to release that energy (like you do whenever it’s time to do science!). The fuel in a gas tank has the potential energy to make the car move.

[/am4show]

Pulsars

Sunday May 9, 2010

A pulsar is a specific type of neutron star, so let’s start there.  Neutron stars are made when a star slightly more massive than our Sun dies and goes supernova.  In a supernova event, large amounts of radiation explodes out from the star, causing a brilliant flash of light which can sometimes outshine an entire galaxy.


At the same time, gravity causes the core of the star to collapse into a neutron star.  Neutron stars are made almost entirely of neutrons (hence the name), and are MUCH smaller in size than their parent stars.  Since a neutron star keeps most of the angular momentum from its parent star but has a significantly smaller radius, it spins with very high rotational speeds.  These speeds typically lead to rotational periods ranging from milliseconds to seconds.


In addition to spinning quickly, neutron stars also commonly have very strong magnetic fields that can accelerate electromagnetic particles and eject them out along the magnetic poles of the star at extremely high velocities.  This results in neutron stars emitting spinning beams of radiation, or light.


[am4show have=’p8;p9;p96;’ guest_error=’Guest error message’ user_error=’User error message’ ]



When a neutron star happens to have its rotation axis oriented so that one or both of its beams of radiation points toward Earth as it rotates, it is called a pulsar.  The name pulsar is a combination of the words “pulsating star”, since the action of the beam of radiation passing over Earth is experienced by us as a pulse of light, much like how one sees pulses of light from a lighthouse.


These pulses are observed on Earth at regular intervals which are associated with a pulsar’s period of rotation.  The faster a pulsar is spinning, the more pulses are measured on Earth in a set amount of time.  This is demonstrated in the above video, with faster-spinning (i.e. more rotations per second) pulsars creating sounds, or chirps, more often than slower-spinning pulsars.


The reason that you can hear many pulsars is because they emit energy in radio wavelengths.  Just like how your radio at home can pick up radio signals and turn them into sound, the radio waves from pulsars are detected here on Earth with radio telescopes – large circular dishes similar to the small ones used on top of people’s houses to receive TV signals from satellites – and converted into sound.  The chirping or drumming sound that you hear in the video is actually created by the pulsar’s spinning beams of energy!


[/am4show]


BEAM Robots

Saturday May 1, 2010

This project is for advanced students.This is one of the coolest applications of renewable energy to come about in recent years. BEAM stands for Biology, Electronics, Aesthetics, and Mechanics. It basically refers to a class of robots that instead of having complicated brains, rely on nervous-system type of sensors to interact with their world.


Some BEAM robots skitter, dance, flash, jump, roll, or walk, and most are solar powered. The result is a fast responding robot made of old cell phone parts that can fit inside your hand. We’ll be making a few different types so you can get a good handle on this type of programming-free, battery-free robotics.


Most BEAM robots use the same solar ‘engine’. The solar cell will convert sunlight into electricity, which will then be stored in our capacitors (think ‘electricity tanks’) until a certain threshold is reached… when the tanks are full, the robot begins to move. This means that you can leave them out all day, and they will sit and collect energy, then turn on by themselves until they run out of juice, then turn off, sit and recharge until they have enough energy to go again… and off they go!


Let’s walk through how to make a BEAM robot. Once you’ve got the hang of it, make a second solar engine from the rest of your parts and add any kind of body you want!


[am4show have=’p9;p49;p108;p103;’ guest_error=’Guest error message’ user_error=’User error message’ ]


You’ll need to get the following materials:


Here’s what you do…


Beam Robot:


[/am4show]


Stirling Engine

Saturday May 1, 2010

This project is for advanced students.This Stirling Engine project is a very advanced project that requires skill, patience, and troubleshooting persistence in order to work right.  Find yourself a seasoned Do-It-Yourself type of adult (someone who loves to fix things or tinker in the garage) before you start working on this project,  or you’ll go crazy with nit-picky things that will keep the engine from operating correctly.  This makes an excellent project for a weekend.


Developed in 1810s, this engine was widely used because it was quiet and could use almost anything as a heat source. This kind of heat engine squishes and expands air to do mechanical work. There’s a heat source (the candle) that adds energy to your system, and the result is your shaft spins (CD).


This engine converts the expansion and compression of gases into something that moves (the piston) and rotates (the crankshaft). Your car engine uses internal combustion to generate the expansion and compression cycles, whereas this heat engine has an external heat source.


This experiment is great for chemistry students learning about Charles’s Law, which is also known as the Law of Volumes, which describes how gases tend to expand when they are heated and can be mathematically written like this:



where V = volume, and T = temperature. So as temperature increases, volume also increases. In the experiment you’re about to do, you will see how heating the air causes the diaphragm to expand which turns the crank.


[am4show have=’p9;p49;p85;p88;p103;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Here’s what you need:


  • three soda cans
  • old inner tube from a bike wheel
  • super glue and instrant dry
  • electrical wire (3- conductor solid wire)
  • 3 old CDs
  • one balloon
  • penny
  • nylon bushing (from hardware store)
  • alcohol burner (you can build one out of soda cans or Sterno canned heat)
  • fishing line (15lb. test or similar)
  • pack of steel wool
  • drill with 1/16″ bit
  • pliers
  • scissors
  • razor
  • wire cutters
  • electrical tape
  • push pin
  • permanent marker
  • Swiss army knife (with can opener option)
  • template
  • HINT: The “circle template” mentioned at 21:57 is actually just a circle traced from the bottom of the soda can onto a sheet of paper

The Stirling heat engine is very different from the engine in your car.  When Robert Stirling invented the first Stirling engine in 1816, he thought it would be much more efficient than a gasoline or diesel engine. However, these heat engines are used only where quiet engines are required, such as in submarines or in generators for sailboats.



Download Student Worksheet & Exercises


Here’s how a Stirling engine is different from the internal-combustion engine inside your car. For example, the gases inside a Stirling engine never leave the engine because it’s an external combustion engine. This heat engine does not have exhaust valves as there are no explosions taking place, which is why Stirling engines are quieter. They use heat sources that are outside the engine, which opens up a wide range of possibilities from candles to solar energy to gasoline to the heat from your hand.


There are lots of different styles of Stirling engines. In this project, we’ll learn about the Stirling cycle and see how to build a simple heat engine out of soda cans.  The main idea behind the Stirling engine is that a certain volume of gas remains inside the engine and gets heated and cooled, causing the crankshaft to turn. The gases never leave the container (remember – no exhaust valves!), so the gas is constantly changing temperature and pressure to do useful work.  When the pressure increases, the temperature also increases. And when the temperature of the gases decreases, the pressure also goes down. (How pressure and temperature are linked together is called the “Ideal Gas Law”.)


Some Stirling engines have two pistons where one is heated by an external heat source like a candle and the other is cooled by external cooling like ice. Other displacer-type Stirling engines has one piston and a displacer. The displacer controls when the gas is heated and cooled.


In order to work, the heat engine needs a temperature difference between the top and bottom of the cylinder. Some Stirling engines are so sensitive that you can simply use the temperature difference between the air around you and the heat from your hand. Our Stirling engine uses temperature difference between the heat from a candle and ice water.


The balloon at the top of the soda can is actually the ‘power piston’ and is sealed to the can.  It bulges up as the gas expands. The displacer is the steel wool in the engine which controls the temperature of the air and allows air to move between the heated and cooled sections of the engine.


When the displacer is near the top of the cylinder, most of the gas inside the engine is heated by the heat source and gas expands (the pressure  builds inside the engine, forcing the balloon piston up). When the displacer is near the bottom of the cylinder, most of the gas inside the engine cools and contracts. (the pressure decreases and the balloon piston is allowed to contract).


Since the heat engine only makes power during the first part of the cycle, there’s only two ways to increase the power output: you can either increase the temperature of the gas (by using a hotter heat source), or by cooling the gases further by removing more heat (using something colder than ice).


Since the heat source is outside the cylinder, there’s a delay for the engine to respond to an increase or decrease in the heat or cooling source. If you use only water to cool your heat engine and suddenly pop an ice cube in the water, you’ll notice that it takes five to fifteen seconds to increase speed. The reason is because it takes time for the additional heat (or removal of heat by cooling) to make it through the cylinder walls and into the gas inside the engine. So Stirling engines can’t change the power output quickly. This would be a problem when getting on the freeway!


In recent years, scientists have looked to this engine again as a possibility, as gas and oil prices rise, and exhaust and pollutants are a concern for the environment. Since you can use nearly any heat source, it’s easy to pick one that has a low-fume output to power this engine. Scientists and engineers are working on a model that uses a Stirling engine in conjunction with an internal-combustion engine in a hybrid vehicle… maybe we’ll see these on the road someday!


Exercises


  1. What is the primary input of energy for the Stirling engine?
  2.  As Pressure increases in a gas, what happens to temperature?
    1. It increases
    2. Nothing
    3. It decreases
    4. It increases, then decreases
  3. What is the primary output of the Stirling engine?

[/am4show]


BEAM Robot: Solar Roller

Saturday May 1, 2010

Note: Brian Cox has created a BEAM Bot kit as an alternative BEAM project.

Brian's BEAM BOT is modeled after small BEAM projects where parts are soldered to each other, but such projects can be difficult to solder.

BEAM Bot uses a standard Printed Circuit Board (PCB) as the frame thus making it easier to assemble.

You can order Brian's BEAM Bot Kit here: fvresearch.com/product/beam-bot .

Click here for Brian's BEAM Bot instructional video (which can be found under Unit 25).

This project is for advanced students.This is one of the coolest applications of renewable energy to come about in recent years. BEAM stands for Biology, Electronics, Aesthetics, and Mechanics. It basically refers to a class of robots that instead of having complicated brains, rely on nervous-system type of sensors to interact with their world.

Some BEAM robots skitter, dance, flash, jump, roll, or walk, and most are solar powered. The result is a fast responding robot made of old cell phone parts that can fit inside your hand. We'll be making a few different types so you can get a good handle on this type of programming-free, battery-free robotics.

[am4show have='p9;p49;p108;p103;' guest_error='Guest error message' user_error='User error message' ]

To make this project, you'll need to get the Solar Roller kit from Solarbotics. You'll also need your soldering equipment and basic tools, like pliers, wire strippers, scissors, and electrical tape.



[/am4show]


BEAM Robot: Trimet

Saturday May 1, 2010

Note: Brian Cox has created a BEAM Bot kit as an alternative to the Trimet project.

Brian's BEAM BOT is modeled after small BEAM projects where parts are soldered to each other, but such projects can be difficult to solder.

BEAM Bot uses a standard Printed Circuit Board (PCB) as the frame thus making it easier to assemble.

You can order Brian's BEAM Bot Kit here: fvresearch.com/product/beam-bot .

Click here for Brian's BEAM Bot instructional video (which can be found under Unit 25).

This project is for advanced students. This is one of the coolest applications of renewable energy to come about in recent years. BEAM stands for Biology, Electronics, Aesthetics, and Mechanics. It basically refers to a class of robots that instead of having complicated brains, rely on nervous-system type of sensors to interact with their world.

Some BEAM robots skitter, dance, flash, jump, roll, or walk, and most are solar powered. The result is a fast responding robot made of old cell phone parts that can fit inside your hand. We'll be making a few different types so you can get a good handle on this type of programming-free, battery-free robotics.

You'll need to get the Trimet Kit from Solarbotics. It has everything you need except the tools for the job (soldering iron, pliers, wire strippers, razor) and paperclips.

Here's what you do:

[am4show have='p9;p49;p108;p103;' guest_error='Guest error message' user_error='User error message' ]


[/am4show]


BEAM Robot: MiniBall

Saturday May 1, 2010

This project is for advanced students.This is one of the coolest applications of renewable energy to come about in recent years. BEAM stands for Biology, Electronics, Aesthetics, and Mechanics. It basically refers to a class of robots that instead of having complicated brains, rely on nervous-system type of sensors to interact with their world.

Some BEAM robots skitter, dance, flash, jump, roll, or walk, and most are solar powered. The result is a fast responding robot made of old cell phone parts that can fit inside your hand. We'll be making a few different types so you can get a good handle on this type of programming-free, battery-free robotics.

[am4show have='p9;p49;p108;p103;' guest_error='Guest error message' user_error='User error message' ]

You'll need to get the MiniBall Kit from Solarbotics. It has everything you need except the tools for the job (soldering iron, pliers, wire strippers, razor), paperclips, and 80mm plastic ball (the kind found at craft stores for making your own holiday ornaments).

Here's what you do:

[/am4show]


Build and Fly a Real Alpha Rocket

Thursday April 22, 2010

If you’ve got an adult who made Estes Rockets as a kid, you’ll definitely want their help when you start your own. The excitement that building rockets creates, the passion that you both can share… it will make your rocketry adventure that much more memorable.


Suppose you already have your adult helper (if not, stop here and get one. You really can’t do this without adult help, because this project involves FIRE.) The first thing you need to do is order your Alpha Rocket Kit. You can order one online or find one at your local hobby shop.


Since this experiment is a Bonus Experiment (it’s a more expensive project, and the parts are not typically in your local grocery store or hardware store…), the materials required are not listed with the main supplies for this set.
[am4show have=’p9;p51;p109;p103;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Here are the supplies you will need to complete this project:



Here are my kids launching rockets! We are sometimes known as the “Rocket Family”…


   
   

National Association of Rocketry Safety Code


The NAR has a great code for safety that you should read and follow to make your rocket launching experience always the best and the safest. You can get a copy of their safety guidelines here.


NAR Model Rocket Safety Code
Revised 2009


  1. Materials. I will use only lightweight, non-metal parts for the nose, body, and fins of my rocket.
  2. Motors. I will use only certified, commercially-made model rocket motors, and will not tamper with these motors or use them for any purposes except those recommended by the manufacturer.
  3. Ignition System. I will launch my rockets with an electrical launch system and electrical motor igniters. My launch system will have a safety interlock in series with the launch switch, and will use a launch switch that returns to the “off” position when released.
  4. Misfires. If my rocket does not launch when I press the button of my electrical launch system, I will remove the launcher’s safety interlock or disconnect its battery, and will wait 60 seconds after the last launch attempt before allowing anyone to approach the rocket.
  5. Launch Safety. I will use a countdown before launch, and will ensure that everyone is paying attention and is a safe distance of at least 15 feet away when I launch rockets with D motors or smaller, and 30 feet when I launch larger rockets. If I am uncertain about the safety or stability of an untested rocket, I will check the stability before flight and will fly it only after warning spectators and clearing them away to a safe distance.
  6. Launcher. I will launch my rocket from a launch rod, tower, or rail that is pointed to within 30 degrees of the vertical to ensure that the rocket flies nearly straight up, and I will use a blast deflector to prevent the motor’s exhaust from hitting the ground. To prevent accidental eye injury, I will place launchers so that the end of the launch rod is above eye level or will cap the end of the rod when it is not in use.
  7. Size. My model rocket will not weigh more than 1,500 grams (53 ounces) at liftoff and will not contain more than 125 grams (4.4 ounces) of propellant or 320 N-sec (71.9 poundseconds) of total impulse. If my model rocket weighs more than one pound (453 grams) at liftoff or has more than four ounces (113 grams) of propellant, I will check and comply with Federal Aviation Administration regulations before flying.
  8. Flight Safety. I will not launch my rocket at targets, into clouds, or near airplanes, and will not put any flammable or explosive payload in my rocket.
  9. Launch Site. I will launch my rocket outdoors, in an open area at least as large as shown in the accompanying table, and in safe weather conditions with wind speeds no greater than 20 miles per hour. I will ensure that there is no dry grass close to the launch pad, and that the launch site does not present risk of grass fires.
  10. Recovery System. I will use a recovery system such as a streamer or parachute in my rocket so that it returns safely and undamaged and can be flown again, and I will use only flameresistant or fireproof recovery system wadding in my rocket.
  11. Recovery Safety. I will not attempt to recover my rocket from power lines, tall trees, or other dangerous places.


[/am4show]


Real Rockets

Tuesday March 23, 2010

Rockets shoot skyward with massive amounts of thrust, produced by chemical reaction or air pressure. Scientists create the thrust force by shoving a lot of gas (either air itself, or the gas left over from the combustion of a propellant) out small exit holes out the back of the nozzles.

Here are two videos of real rockets being tested. The second video uses a special type of photography to see the shock waves (you will learn more about how that's done in Unit 9).

For every action, there is equal and opposite reaction. If flames shoot out of the rocket downwards, the rocket itself will soar upwards. It’s the same thing if you blow up a balloon and let it go—the air inside the balloon goes to the left, and the balloon zips off to the right. They both follow Newton's Third Law: for every action, there is an equal and opposite reaction.

What you're looking at in the video below is exactly the kind of work I did as a graduate student in college when I was 21. The end of a rocket nozzle is on the right side, and you're looking at supersonic air (made visible by a special type of photography called 'Schlieren') as a rushes past from right to left. The thick white lines are shock waves, which are lines where the pressure drop is huge. When the flow is fast enough (around Mach 2 and up), you'll see nicely shaped 'Mach Diamonds' form.

Scientists use these images to tell how well the engines will perform at high-speed flight. One of the greatest aeronautical engineers, Kelly Johnson, who founded Skunkworks at Lockheed, said the greatest compliment he ever received was when a friend commented: "It's amazing... he can actually see airflow." This is what Johnson could visualize in his mind simply because he understood the fundamentals of aerodynamics:


Basic Circuits

Sunday March 7, 2010

An electrical circuit is like a raceway or running track at school.  The electrons (racecars) zip around the race loop (wire circuit) superfast to make stuff happen. Although you can’t see the electrons zipping around the circuit, you can see the effects: lighting up LEDs, sounding buzzers, clicking relays, etc.

There are many different electrical components that make the electrons react in different ways, such as resistors (limit current), capacitors (collect a charge), transistors (gate for electrons), relays (electricity itself activates a switch), diodes (one-way street for electrons), solenoids (electrical magnet), switches (stoplight for electrons), and more.  We’re going to use a combination diode-light-bulb (LED), buzzers, and motors in our circuits right now.

A CIRCUIT looks like a CIRCLE.  When you connect the batteries to the LED with wire and make a circle, the LED lights up.  If you break open the circle, electricity (current) doesn’t flow and the LED turns dark.

LED stands for “Light Emitting Diode”.  Diodes are one-way streets for electricity – they allow electrons to flow one way but not the other.

Remember when you scuffed along the carpet?  You gathered up an electric charge in your body.  That charge was static until you zapped someone else.  The movement of electric charge is called electric current, and is measured in amperes (A). When electric current passes through a material, it does it by electrical conduction. There are different kinds of conduction, such as metallic conduction, where electrons flow through a conductor (like metal) and electrolysis, where charged atoms (called ions) flow through liquids.

[am4show have='p8;p9;p20;p47;p106;p76;p97;p58;' guest_error='Guest error message' user_error='User error message' ]

Here's what you need:

  • 2 AA heavy duty (carbon) batteries - Do not use alkaline or rechargeable batteries
  • AA battery case
  • 2 alligator wires
  • LEDs (any you choose is fine)

Download Student Worksheet & Exercises

Be alert for:

1. Batteries inserted into the case the wrong way!

2. LED in the wrong way (LEDs are picky about plus and minus - they are POLARIZED)

3. Is there a metal-to-metal connection?  (You're not grabbing ahold of the plastic insulation, are you?)

4. Bad wires can cause headaches - if all else fails, then swap out your alligator clip lead wires for new ones.

Exercises

  1. What does LED stand for?
  2. Does it matter which way you wire an LED in a circuit?
  3. Does the longer wire on the LED connect to plus (red) or minus (black)?
  4. Do you need to hook up batteries to make a neon bulb light up?  Why or why not?
  5. What's the difference between a light bulb and your LED?
  6. What is the difference between a bolt of lightning and the electricity in your circuit?
  7. What is the charge of an electron?

[/am4show]


Steerable Waterbot

Sunday March 7, 2010

After you make the Waterbot, you can create a two-motor version that you can steer using a remote control!


[am4show have=’p8;p9;p98;p108;’ guest_error=’Guest error message’ user_error=’User error message’ ]



The next step is to wire up your remote-control for this project.


Still want more? For our advanced students, you can check out the Underwater Robot project!
[/am4show]


Artbot

Sunday March 7, 2010

This is a fun variation of the Jigglebot that uses markers for legs so it can scrawl you out a masterpiece as it entertains you with its curious dance.
[am4show have=’p8;p9;p98;p108;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials:


  • foam block
  • 5-8 markers
  • AA battery case with AA batteries
  • alligator clips
  • 3V DC motor
  • wood clothespin
  • hot glue gun
  • scissors or razor


[/am4show]


Conductivity Testers

Sunday March 7, 2010

switch-zoomMake yourself a grab bag of fun things to test: copper pieces (nails or pipe pieces), zinc washers, pipe cleaners, Mylar, aluminum foil, pennies, nickels, keys, film canisters, paper clips, load stones (magnetic rock), other rocks, and just about anything else in the back of your desk drawer.


Certain materials conduct electricity better than others. Silver, for example, is one of the best electrical conductors on the planet, followed closely by copper and gold. Most scientists use gold contacts because, unlike silver and copper, gold does not tarnish (oxidize) as easily. Gold is a soft metal and wears away much more easily than others, but since most circuits are built for the short term (less than 50 years of use), the loss of material is unnoticeable.
[am4show have=’p8;p9;p20;p47;p76;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Modify your basic LED circuit into a Conductivity Circuit by removing one clip lead from the battery and inserting a third clip lead to the battery terminal. The two free ends are your new clips to put things in from the grab bag. Try zippers, metal buttons, barrettes, water from a fountain, the fountain itself, bike racks, locks, doorknobs, unpainted benches… you get the idea!


Here’s what you need:


  • 2 AA batteries
  • AA battery case
  • 3 alligator wires
  • LEDs (any you choose is fine)
  • paper clip
  • penny
  • other metal objects around your house (zippers, chairs, etc…)


Why does metal conduct electricity?

Why does metal, not plastic, conduct electricity? Imagine you have a garden hose with water flowing through it. The hose is like the metal wire, and the water is like the electric current. Trying to run electricity through plastic is like filling your hose with cement. It’s just the nature of the material.



Download Student Worksheet & Exercises


Exercises


  1.       Name six materials that are electrically conductive.
  2.        What kinds of materials are conductors and insulators?
  3.      Can you convert an insulator into a conductor? How?
  4.        Name four instances when insulators are a bad idea to have around.
  5.      When are insulators essential to have?

[/am4show]


Simple Switches

Sunday March 7, 2010

knifeswitchWhen you turn on a switch, it’s difficult to really see what’s going on… which is why we make our own from paperclips, brass fasteners, and index cards.


Kids can see the circuit on both sides of the card, so it makes sense why it works (especially after doing ‘Conductivity Testers’).


SPST stands for Single Pole, Single Throw, which means that the switch turns on only one circuit at a time. This is a great switch for one of the robots we’ll be making soon, as it only needs one motor to turn on and off.
[am4show have=’p8;p9;p20;p47;p106;p108;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Think of this switch like a train track. When you throw the switches one way, the train (electrons) can race around the track at top speed. When you turn the switch to the OFF position, it’s like a bridge collapse for the train – there’s no way for the electrons to jump across from the brass fastener to the paper clip. When you switch it to the ON position (both sides), you’ve rebuilt the bridges for the train (electrons).


Troubleshooting: The two tabs on the back of the motor are the places to clip in the power from the battery pack. Since these motors spin quickly and the shaft is tiny, add a piece of tape to the shaft to see the spinning action more clearly.


Kids can make their own switches so they can trace the path the electricity takes with a finger. See what you think about this SPST:


Here’s what you need:


  • 2 AA batteries
  • AA battery case
  • 3 alligator wires
  • index card
  • 2 brass fasteners
  • paper clips
  • buzzer, motor, or LED


Download Student Worksheet & Exercises


Exercises


  1.  If you want to reverse the spin direction of a motor without using a switch, what can you do?
  2.  A simple switch can be made out of what kinds of materials?
  3.  How would you make your SPST switch an NC (normally closed) switch?
  4.  How did you have to connect your circuit in order for both the LED and motor to work at the  same time? Draw it here:
  5.  Draw a picture of your experiment that explains how the SPST switch works, and show how      electricity flows through your circuit:

Extra Credit (for students who have completed Part 3):


  1. Draw a picture of your experiment that explains how the DPDT switch works in your circuit and show how to wire up the circuit.

[/am4show]


Robotic Cookie Snatcher

Sunday March 7, 2010

cookie-snatcher2 001Are cookies out of reach in your house? When I was a small kid, the top of the refrigerator seemed MILES away… until I built a robot arm out of toothbrushes, popsicle sticks, and cardboard to reach it for me!


I’ve upgraded my old idea to include a motorized linear actuator so you can see how real robot engineers create linear motion (back and forth along a straight line) from a spinning motor. The motor AND nut both need to pivot for the claw to work, so take special note as to how the linear actuator (the scissors-looking thing) is built.


[am4show have=’p8;p9;p20;p47;p108;p98;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Here’s what you need:


  • piece of cardboard
  • two fat popsicle sticks
  • two toothbrushes or spoons or other things you can use as grippers
  • two large paper clips
  • four brass fasteners
  • one LONG bolt with nut (either a hexnut or wingnut)
  • one 1.5-3VDC hobby motor
  • two AA battery cases with batteries
  • alligator clip wires
  • 3 thumbtacks
  • cork from a wine bottle or small plastic gear from an old toy that fits onto your motor shaft
  • scissors
  • hot glue gun and glue sticks


Make sure that the motor can pivot on the popsicle stick or it will jam and won’t move up the screw threads. This is the basis for many real, working industrial robots that need to lift very heavy loads.


[/am4show]


Wiring Up Motors

Sunday March 7, 2010

Imagine you have two magnets. Glue one magnet on an imaginary record player (or a ‘lazy susan’ turntable) and hold the other magnet in your hand. What happens when you bring your hand close to the turntable magnet and bring the north sides together?


The magnet should repel and move, and since it’s on a turntable, it will circle out of the way. Now flip your hand over so you have the south facing the turntable. Notice how the turntable magnet is attracted to yours and rotates toward your hand. Just as it reaches your hand, flip it again to reveal the north side. Now the glued turntable magnet pushes away into another circle as you flip your magnet over again to attract it back to you. Imagine if you could time this well enough to get the turntable magnet to make a complete circle over and over again… that’s how a motor works!


After you get the buzzer and the light or LED to work, try spinning a DC motor:


[am4show have=’p8;p9;p20;p47;p106;p76;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Here’s what you need:


  • 2 AA batteries
  • AA battery case
  • 2 alligator wires
  • 1.5-3V DC motor
  • optional: propeller


[/am4show]


Superfast Bug Bot

Sunday March 7, 2010

bugbot2 001This project is advanced students. If you like tiny robots, then this one is for you! Powered by cheap hobby motors, this fast little robot zips ’round and avoids obstacles using momentary switches and an idler wheel for a tail.


I recommend watching the entire video first, then rewind and watch again, this time building as you go. Make sure you have all your parts laid out ahead of time, or you’ll get frustrated partway through if you have to stop. You will need a soldering iron to make this project.


Here’s what you do:
[am4show have=’p9;p47;p103;’ guest_error=’Guest error message’ user_error=’User error message’ ]


You will need to find:


Tools:


  • Wire strippers
  • Pliers
  • Soldering iron, solder, stand


[/am4show]


Underwater R.O.V. Robot

Sunday March 7, 2010

rov12This project is for advanced students.


Up until 200 years ago, people thought the oceans were bottomless.  The diving bell was one of the first recorded attempts at undersea exploration, and was simply a five-foot inverted cup with viewing holes on a platform that lowered into the water, which allowed people to breathe the trapped air inside… until they ran out of air.  Leonardo da Vinci draw several sketches of underwater submersibles, and in the 1700s, John Lethbridge invented a long wooden cylinder with glass ends as one of the first diving units to reach 60 feet.


In 1930, two explorers used the bathysphere (a giant ball with windows) reached 1,428 feet below the surface, which was later followed by the bathyscape (deep diving vessel) that reached the deepest part of the Pacific Ocean, the Marianas Trench, at 35,800 feet in 1960.


The ROVs first made their appearance in the late 1960s, when military and offshore drilling required deeper dives.  In the late 1980s, scientists needed a way to explore the remains of the Titanic, and a lower-cost, lighter weight version design was developed. ROVs are designed to be remote extensions of the operator.


One of the biggest challenges with deep-diving underwater vessels is keeping the tremendous pressure from crumpling the frame.  The project we’re going to design is meant for swimming pools and smaller lakes. When designing your underwater vehicle, you’ll need to pay close attention to the finer details such as waterproofing the electrical motors and maintaining proper balance so that your robot doesn’t flip over or swim in circles.


Learn about thruster motors, create the chassis, and build the controller for these super-popular underwater robots that really swim in water! A fantastic project for parents and kids to work together on. Your underwater robot will move in all six directions and utilizes a 12V power source.


[am4show have=’p9;p47;p108;p103;’ guest_error=’Guest error message’ user_error=’User error message’ ]


You are about to embark on the adventure of creating and operating your own ROV underwater robot.  As with all Supercharged Science educational items, we want kids to discover that science isn’t in the special parts that come with a kit, but rather in the imagination and skill of the kid building it.  We strive to avoid parts that are specially made just for a kit, molded plastic pieces, etc. and instead use parts that any kid could buy from the store.  This means that kids can feel free to change things around, use their own ideas to add improvements and whatever else their imagination can come up with.  So on this note, let’s get started.


WARNING: This project is intended for kids over age 12, and requires adult supervision.  Here are things to keep in mind:


  1. The soldering iron reaches temperatures over 750○ F.  It can obviously cause severe burns and serious injury.  Always put it in the stand when not in use.  Don’t look away while using it. Unplug it as soon as you’re done and set it in a place to cool where it won’t get knocked over.
  2. Solder sometimes contains lead.  Just don’t get it near your face and wash your hands when you’re done touching it.  Plus, the usual warning that lead causes disease, it’s toxic, don’t feet it to you pets and keep it away from children.
  3. The thruster motors in this kit are VERY powerful.  The propellers (when turning) will easily cut through skin and flesh if you touch them! (Don’t be fooled because they’re plastic).  NEVER touch them with anything when they are turning.  Treat them like you would a power saw.  Always disconnect power before working on them (short circuits can make them start unexpectedly).
  4. PLEASE use common sense.  Think like a real scientist: If something seems like it might be dangerous, it probably is.  The real world doesn’t have warnings on everything that could possibly hurt you.  I ask that you apply similar good judgment in using this kit.  If you’re not sure, ASK for help.  Ask a parent. And parents, if you need help, email or call us.
  5. Okay, I’m required to say this one: This kit contains small parts, plastic bags and other choking hazards.  Children under 3 years of age should not be allowed to touch it.  (Obviously this is true since it’s meant for kids over 12.)
Omit the 2″ float pieces and instead put a pool noodle around the 1/2″ PVC, and also skip the toilet seal wax for sealing the thrusters (not sure if the video has this step or if we omitted it already) and just use straight hot glue. The frame does not need to be airtight, so if you’re concerned about fumes, just use hot glue for the entire project.
UPDATED ROV DESIGN: Omit the 2″ float pieces and instead put a pool noodle secured with zip ties around the 1/2″ PVC, and seal each thruster with hot glue. The frame does not need to be airtight, so if you’re concerned about fumes from the PVC glue, just use  hot glue for the entire project.

Materials:


The parts you’ll need are as follows:


Glue & Fasteners


  • Superglue (0.5 oz. bottle or more)
  • Hot glue gun and extra glue sticks
  • Tube of silicone sealant or caulking
  • Petroleum jelly (Vaseline)
  • 6 pcs. #6 x ½” stainless steel or brass sheet metal screws
  • 6 pc. #6 stainless steel washers
  • 10 pcs. 6” x 3/16” zip ties
  • Old newspapers to work on
  • Paper towels to clean up with

Frame Parts


  •  5 ft. of ½” schedule 40 PVC pipe (Have it cut into these pieces at the store)
    • 6 pcs. 1.5″ long
    • 8 pcs. 4″ long
    • 2 pcs. 6.5″ long
  • 10 pcs. ½” schedule 40 PVC 90-degree elbows
  •  4 pcs. ½” schedule 40 PVC tee’s
  •  2 ft. of 2” schedule 40 PVC pipe (Have it cut into two 6″ pieces at the store)
  •  4 pcs. 2” schedule 40 PVC end caps
  • 3 thruster housings (plastic vials like film canisters… something that the hobby motors can fit into snugly)
  • 3 pieces of 1” metal semicircular conduit straps (w/2 screw holes. 1” conduit)
  • 10” x 6.5” piece of plastic hardware cloth (1/4” squares) – it looks like a plastic mesh grid. If you have chicken wire on hand, then you can use that instead.

Electrical parts


  • Three 12V DC motors 
  • 3 thruster propellers (drill out with 3/32” holes) – boat propellers from a hobby store work great
  • 3 DPDT center-off screw terminal switches
  • Electrical tape (good quality) OR 2 pcs. #31 wire nut connectors
  • 30 ft. of “CAT-3” (or “CAT-5”) telephone/network cable (8-conductor or 4-pair, AWG 24)
  • Rectangular project box  (Approx. 4” x 6” x 3”)
  • 12V Battery (two 6-volt lantern batteries, an old motorcycle or car battery or an “automotive jump starter” rechargeable power source)

Tools


  • Wire strippers
  • Long nose pliers
  • Soldering iron & stand with solder
  • An electric drill
  • Assorted drill bits (Specifically: 3/32”, 1/8”, 1/4”)
  • Razor knife
  • Hack saw or PVC pipe cutter
  • Flathead screwdrivers
  • Scissors
  • #120 sandpaper
  • A ruler or measuring tape

Okay, so you’re ready to go.  Oh, a couple of notes.  First, if your thruster housings are not snug enough in the pipe clamps, just wrap electrical tape around them a few times to add a little bit of extra thickness.  One other thing.  You may choose to solder alligator clips to your battery wires to make them easier to connect.  Just clip the alligator clip on something large to open its jaws, slip off the rubber part and solder your wire on.


Happy Exploring!



Learn how to turn this project into a winning Science Fair Project!
[/am4show]


Dimmers and Motor Speed Controllers

Sunday March 7, 2010

potSo now you know how to hook up a motor, and even wire it up to a switch so that it goes in forward and reverse. But what if you want to change speeds? This nifty electrical component will help you do just that.


Once you understand how to use this potentiometer in a circuit, you’ll be able to control the speed of your laser light show motors as well as the motors and lights on your robots. Ready?


[am4show have=’p8;p9;p20;p47;p106;p108;p76;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Here’s what you need:


  • 2 AA batteries
  • AA battery case
  • 3 alligator wires
  • potentiometer
  • 1.5-3V DC motor
  • LED (any you choose)


Download Student Worksheet & Exercises


Exercises


  1. How does a potentiometer work?
  2. Does the potentiometer work differently on the LED and the motor?
  3. Name three places you’ve used potentiometers in everyday life.
  4. How do you think you might wire up an LED, switch, and potentiometer?

[/am4show]


Forward and Reverse Motor Control

Sunday March 7, 2010

Once you’ve made a a simple switch, you’re ready to use more advanced electrical components, such as the DPDT switch you picked up from an electronics store (refer to shopping list for this section). When you wire up this nifty device, you’ll be able to get your motors to go forward, reverse, and stop… all with the flip of a switch.


You can use this component along with a potentiometer so you can not only control the direction but also the speed of a motor, like in a robot or laser light show. And don’t feel limited on using this switch just with motors – it works with bi-polar LEDs and other things as well.  For example, you can hook this up so that when it’s in the UP position, the buzzer sounds, and the DOWN position makes the headlights go on. Are you ready to learn how to wire this one up?


[am4show have=’p8;p9;p20;p47;p106;p108;p97;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Click here to learn how to incorporate this switch into your robot by making a simple remote control.
[/am4show]


Advanced Static Electricity Experiments

Sunday March 7, 2010

You can use the idea that like charges repel (like two electrons) and opposites attract to move stuff around, stick to walls, float, spin, and roll. Make sure you do this experiment first.


I’ve got two different videos that use positive and negative charges to make things rotate, the first of which is more of a demonstration (unless you happen to have a 50,000 Volt electrostatic generator on hand), and the second is a homemade version on a smaller scale.


Did you know that you can make a motor turn using static electricity? Here’s how:


[am4show have=’p8;p9;p20;p47;p76;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Download Student Worksheet & Exercises


Here’s how the electrostatic machine works – you will need:


  • a yardstick
  • spoon
  • balloon


How does it work? Different parts of the atom have different electrical charges. The proton has a positive charge, the neutron has no charge (neutron, neutral get it?) and the electron has a negative charge. These charges repel and attract one another kind of like magnets repel or attract. Like charges repel (push away) one another and unlike charges attract one another.


So if two items that are both negatively charged get close to one another, the two items will try to get away from one another. If two items are both positively charged, they will try to get away from one another. If one item is positive and the other negative, they will try to come together.


How do things get charged? Generally things are neutrally charged. They aren’t very positive or negative. However, occasionally (or on purpose as we’ll see later) things can gain a charge. Things get charged when electrons move. Electrons are negatively charged particles. So if an object has more electrons than it usually does, that object would have a negative charge. If an object has less electrons than protons (positive charges), it would have a positive charge.


How do electrons move? It turns out that electrons can be kind of loosey-goosey. Depending on the type of atom they are a part of, they are quite willing to jump ship and go somewhere else. The way to get them to jump ship is to rub things together.


Remember, in static electricity, electrons are negatively charged and they can move from one object to another. This movement of electrons can create a positive charge (if something has too few electrons) or a negative charge (if something has too many electrons). It turns out that electrons will also move around inside an object without necessarily leaving the object. When this happens the object is said to have a temporary charge.


Try this: Blow up a balloon. When you rub the balloon on your head, the balloon is now filled up with extra electrons, and now has a negative charge. Now stick it to a wall— to create a temporary charge on a wall.


Opposite charges attract right? So, is the entire wall now an opposite charge from the balloon? No. In fact, the wall is not charged at all. It is neutral. So why did the balloon stick to it?


The balloon is negatively charged. It created a temporary positive charge when it got close to the wall. As the balloon gets closer to the wall, it repels the electrons in the wall. The negatively charged electrons in the wall are repelled from the negatively charged electrons in the balloon.


Since the electrons are repelled, what is left behind? Positive charges. The section of wall that has had its electrons repelled is now left positively charged. The negatively charged balloon will now “stick” to the positively charged wall. The wall is temporarily charged because once you move the balloon away, the electrons will go back to where they were and there will no longer be a charge on that part of the wall.


This is why plastic wrap, Styrofoam packing popcorn, and socks right out of the dryer stick to things. All those things have charges and can create temporary charges on things they get close to.


Want to purchase an electrostatic machine? Here’s a link to the one used in the video called a Wimshurst Machine which makes sparks up to 4″ long. For younger kids, we recommend this fun hand-held, non-shocking electrostatic generator.


Exercises


  1.  What happens if you rub the balloon on other things, like a wool sweater?
  2.  If you position other people with charged balloons around the table, how long can you keep  the yardstick going
  3.  Can we see electrons?
  4.  How do you get rid of extra electrons?
  5.  Why do you think the yardstick moved?
  6.  What would happen if you use both a positively charged object and a negatively charged  object to make the yardstick move?

[/am4show]


Alien Detector (Advanced)

Sunday March 7, 2010

fet1This simple FET circuit is really an electronic version of the electroscope. This “Alien Detector” is a super-sensitive static charge detector made from a few electronics parts. I originally made a few of these and placed them in soap boxes and nailed the lids shut and asked kids how they worked. (I did place a on/off switch poking through the box along with the LED so they would have ‘some’ control over the experiment.)


This detector is so sensitive that you can go around your house and find pockets of static charge… even from your own footprints! This is an advanced project for advanced students.


You will need to get:


[am4show have=’p9;p47;p76;p103;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Download Student Worksheet & Exercises


After you’ve made your charge detector, turn it on and comb your hair, holding the charge detector near your head and then the comb. You’ll notice that the comb makes the LED turn off, and your head (in certain spots) makes the LED go on. So it’s a positive charge static detector… this is important, because now you know when the LED is off, the space you’re detecting is negatively charged, and when it’s lit up, you’re in a pocket of positively charged particles. How far from the comb does your detector need to be to detect the charge? Does it matter how humid it is?


You can take your detector outdoors, away from any standing objects like trees, buildings, and people, and hold it high in the air. What does the LED look like? What happens when you lower the detector closer to the ground? Raise it back up again to get a second reading… did you find that the earth is negative, and the sky is more positive?


You can increase the antenna sensitivity by dangling an extra wire (like an alligator clip lead) to the end of the antenna. Because thunderstorms are moving electrical charges around (negative charges downwards and positive charges upwards), the earth is electrified negatively everywhere. During a thunderstorm, the friction caused by the moving water molecules is what causes lightning to strike! (But don’t test your ideas outside in the wide open while lightening is striking!)


Exercises


  1. When the LED is on, what do you think it means?
  2. Does the LED turning off detect anything?
  3. Do aliens like humidity?
  4. How does this alien detector really work?

[/am4show]


Remote Controls I

Sunday March 7, 2010

rc22Radio control (RC) is a 100 year-old technology. RC requires both a transmitter and a receiver. The control box sends commands to the robot the same way you change channels on the TV with the remote.

The difference between RC (radio control) and IR (infrared control) is in the frequency of the signals. With the radio controller, the light waves that carry the command information are lower energy, lower frequency signals. The TV remote uses higher energy, higher frequency infrared signals called CIR (consumer infrared).

Both RC and CIR require circuit design at a college graduate level. However, wired remote controls are well within the reach of any young budding scientist.

[am4show have='p8;p9;p20;p47;p106;p108;p98;' guest_error='Guest error message' user_error='User error message' ]

By simply removing both the battery pack and switch assembly from the robot, stuffing them in a box, and extending the wires from the box to the robot, you’ve got a wired remote control and a lightweight (and usually faster-moving) robot.

Simple remote controls are a great addition for both the waterbot and race cars. Once the kids build the robot and they’ve gotten over the initial “WOW!” factor, they’ll probably wonder how to turn it off so they can work on it further.

This is an excellent place for a question… “How are you going to turn the motor on and off easily?”

Use the simple SPST switch for these two robots and use 10’ long wires (flexible one-line (2-wire) telephone cable works well).

Materials:

  • your robot that you want to control (use any from this section)
  • index card
  • 2 brass fasteners
  • 1 paper clip
  • 2 additional alligator clip lead wires
  • optional: plastic soap container
  • optional: drill with drill bits

Advanced Tip: When you've mastered this switch, you can substitute the DPDT switch in your robot - this is the switch we use in the underwater ROV robot experiment.

[/am4show]


Remote Controls II

Sunday March 7, 2010

If you've made the waterbot, you can use this wired remove to make the motor turn both forward and reverse. All you need is an extra set of wires (telephone cable with two wires in it work great, or else twist two long wires together... they can be as long as you want.) Enclose the whole thing in a plastic box (I like to use tupperware or a soap box) and drill three holes in the top for the brass fasteners and one in the side for the wire and you're all set!

Materials:

  • your robot that you want to control (use any from this section)
  • index card
  • 3 brass fasteners
  • 1 paper clip
  • 4 additional alligator clip lead wires
  • optional: plastic soap container
  • optional: drill with drill bits

[am4show have='p8;p9;p20;p47;p106;p108;p98;' guest_error='Guest error message' user_error='User error message' ]

[/am4show]


Spectrometer

Wednesday February 3, 2010

spectrometer2Spectrometers are used in chemistry and astronomy to measure light. In astronomy, we can find out about distant stars without ever traveling to them, because we can split the incoming light from the stars into their colors (or energies) and “read” what they are made up of (what gases they are burning) and thus determine their what they are made of. In this experiment, you’ll make a simple cardboard spectrometer that will be able to detect all kinds of interesting things!


SPECIAL NOTE: This instrument is NOT for looking at the sun. Do NOT look directly at the sun. But you can point the tube at a sheet of paper that has the sun’s reflected light on it.


Usually you need a specialized piece of material called a diffraction grating to make this instrument work, but instead of buying a fancy one, why not use one from around your house?  Diffraction gratings are found in insect (including butterfly) wings, bird feathers, and plant leaves.  While I don’t recommend using living things for this experiment, I do suggest using an old CD.


CDs are like a mirror with circular tracks that are very close together. The light is spread into a spectrum when it hits the tracks, and each color bends a little more than the last. To see the rainbow spectrum, you’ve got to adjust the CD and the position of your eye so the angles line up correctly (actually, the angles are perpendicular).


You’re looking for a spectrum (the rainbow image at left) – this is what you’ll see right on the CD itself. Depending on what you look at (neon signs, chandeliers, incandescent bulbs, fluorescent bulbs, Christmas lights…), you’ll see different colors of the rainbow. For more about how diffraction gratings work, click here.


Materials:


  • old CD
  • razor
  • index card
  • cardboard tube

[am4show have=’p8;p9;p19;p46;p105;p83;p89;p91;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Download Student Worksheet & Exercises


Find an old CD and a cardboard tube at least 10 inches long.  Cut a clean slit less than 1 mm wide in an index card or spare piece of cardboard and tape it to one end of the tube.  Align your tube with the slit horizontally, and on the top of the tube at the far end cut a viewing slot about one inch long and ½” inch wide.  Cut a second slot into the tube at a 45 degree angle from the vertical away from the viewing slot.  Insert the CD into this slot so that it reflects light coming through the slit into your eye (viewing slot).


Aim the 1 mm slit at a light source such as a fluorescent light, neon sign, sunset, light bulb, computer screen, television, night light, candle, fireplace… any light source you can find.  Look through the open hole at the light reflected off the compact disk (look for a rainbow in most cases) inside the cardboard tube.


Troubleshooting: This is a quick and easy way to bypass the need for an expensive diffraction grating. Use your spectrometer to look at computer screens, laptops, night lights, neon lights, candles, campfires, fluorescent lights, incandescent lights, LEDs, stoplights, street lights, and any other light sources you can find, even the moon through a telescope.


To make a CALIBRATED Spectrometer, go here.


Exercises


  1. Name three more light sources that you think might work with your spectroscope.
  2.   Why is there a slit at the end of the tube instead of leaving it open?

[/am4show]


Laser Basics

Wednesday February 3, 2010

Did you know that the word LASER stands for Light Amplification by Stimulated Emission of Radiation? And that a MASER is a laser beam with wavelengths in the microwave part of the spectrum? Most lasers fire a monochromatic (one color) narrow, focused beam of light, but more complex lasers emit a broad range of wavelengths at the same time.


In 1917, Einstein figured out the basic principles for the LASER and MASER by building on Max Planck’s work on light. It wasn’t until 1960, though when the first laser actually emitted light at Hughes Research Lab. Today, there are several different kinds of lasers, including gas lasers, chemical lasers, semiconductor lasers, and solid state lasers. One of the most powerful lasers ever conceived are gamma ray lasers (which can replace hundreds of lasers with only one) and the space-based x-ray lasers (which use the energy from a nuclear explosion) – neither of these have been built yet!


[am4show have=’p8;p9;p19;p46;p99;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Gas lasers pump different types of gases to get different laser colors such as the red HeNe (Helium-Neon laser), the high-powered CO2 lasers that they can melt through metal, the blue-green argon-ion, the UV lasers that use nitrogen, and the metallic-gas combination such as He-Ag lasers (helium and silver) and Ne-Cu (neon and copper) which emit a deep violet beam.


But what about lasers used everyday? The lasers we’re going to be using are semiconductor lasers that use a small laser diode to emit a beam. They are the same lasers that are in the grocery store scanners, pen laser pointers and key chain lasers. Usually a class I or II laser, these pose minimal safety risk and are safe to use in our experiments. Here’s what you need to know:


Materials:


  • laser (A key-chain laser works great. Do NOT use green lasers, which can only be used outdoors.)
  • dark room
  • old CD
  • cut-crystal (wine glasses, fancy vases, etc) with adult help
  • microscope slide or window
  • cellophane and nail polish (red, green, and blue are optimal and used again in the Light Wave experiments)
  • feather
  • two pairs of polarized sunglasses
  • frosted incandescent light bulb


Before we start building our laser projects, just play with it first. Turn off the lights at night and take your laser on a hunt around the house to see what happens when you shine it on or through different things. Here are some ideas to try:


1. Shatter the Beam: Shine your beam over the surface of an old CD. Does it work better with a scratched or smoother surface? You should see between 5-13 reflections off the surface of the CD, depending on where you shine it and how well the “seeing” conditions are.


2. Beam Scatter: Pass the laser beam through several cut-crystal objects such as wine glasses or clear glass vases. Is there a difference between clear plastic or glass, smooth or multi-faceted? Try an ice cube, both frosted and wet (clear).


3. Split the Beam: Shine the laser beam through a flat piece of glass, such as a window. Can you find the pass-through beam as well as a reflected beam? Windows and clear plastic containers will split your beam in two.


What’s going on? When you shine your laser beam through glass (like a window) or plastic (like a soda bottle filled with water and a tiny bit of cornstarch), it splits into two beams – one that passes through, and the other that internally reflects back. You can see these reflections in a darkened fog-filled room.


4. Colored Filters: Paint a piece of cellophane or stiff clear plastic with nail polish (or use colored filters) to put in the laser beam.


5. Diffraction Grating: You can make a quick diffraction grating by using a feather in the beam.


6. Polarization: If you have polarizer filters, use two. You can substitute two pairs of sunglasses. Just make sure they are polarized lenses (most UV sunglasses are). Place both lenses in the beam and rotate one 90 degrees. The lenses should block the light completely in one configuration and allow it to pass-through the other way.


Why does this happen? Polarization is a way of filtering light. Try this: in a shallow pan filled with water, make a few waves and notice how they travel from one side of the pan to the other. Now add a plastic comb, and notice how the waves stop when they hit the comb – not many pass through to the other side (watch out for the waves that creep around the edges – we’re focusing on the pass-through waves only). The comb are the sunglasses, and the water waves are the light waves.


Add a second comb at 90 degrees from the first (as you did with the sunglasses) so it resembles a mesh screen, and notice now how NONE of the waves make it through the comb array. Polarization can filter out various amounts of light, depending on the angle the combs make with each other (90 degrees apart equals total block-out).


7. Light Bulbs: In the dark, aim your laser at a frosted incandescent light bulb. The bulb will glow and have several internal reflections! What other types of light bulbs work well?


Learn more! Read up about lasers here.


[/am4show]


Laser Maze

Wednesday February 3, 2010

By using lenses and mirrors, you can bounce, shift, reflect, shatter, and split a laser beam. Since the laser beam is so narrow and focused, you’ll be able to see several reflections before it fades away from scatter. Make sure you complete the Laser Basics experiment first before working with this experiment.


You’ll need to make your beam visible for this experiment to really work.  There are several different ways you can do this:


[am4show have=’p8;p9;p19;p46;p89;p99;’ guest_error=’Guest error message’ user_error=’User error message’ ]


1. Take your laser with you into a steamy bathroom (which has mirrors!) after a hot shower.  The tiny droplets of water in the steam will illuminate your beam. (Psst! Don’t get the laser wet!)


2. If you have carpet, shine your laser under the bed while stomping the floor with your hand.  The small particles (dust bunnies?) float up so you can see the beam. Some parents aren’t going to like this idea, sooo….


3. Drop a chunk of dry ice (use gloves!) into a bowl of water and use the fog to illuminate the beam.  The drawback to this is that you need to keep adding more dry ice as it sublimates (goes from solid to gas) and replacing the water (when it gets too cold to produce fog).


Materials:


  • large paper clips
  • brass fastener
  • index card
  • small mirrors (mosaic-type work well)


Download Student Worksheet & Exercises


Here’s what you do: Open up each paper clip into the “L” shape.  Insert a brass fastener into one U-shape leg and punch it through the card.  Hot glue (or tape) one square mirror to the other end of the L-bracket.  Your mirror should be upright and able to rotate.  Do this with each mirror.  (You can alternatively mount each mirror to a one-inch wooden cube as shown in the video.)


Turn on the laser adjust the mirrors to aim the beam onto the next mirror, and the next!  Turn down the lights first and use any one of the methods mentioned above to make your laser beam visible.


What’s happening? The mirrors are bouncing the laser beam to each other, and the effect shows up when you dim the lights and add fog or dust particles to help illuminate the beam.  A laser beam is a highly focused beam of light, and you can direct that light and bounce it off mirrors!


Why can’t I see the beam normally? The reason you can’t see the laser beam without the help of a steamy room, dirty carpet, or fog machine is that your eyes are tuned for green light, not red (which is why you can see the beam from a green laser at night).


Exercises


  1.   The word LASER is actually an acronym. What does it stand for?
  2. What type of laser did we use in our experiment?
  3. Why can’t we see the laser beams without the help of steam, dirty carpet, etc.?

[/am4show]


Easy Laser Light Show

Wednesday February 3, 2010

Lasers are cool, but what can you do with one? This is a great introductory activity into what lasers are, how they work, and how different mediums (like glass, feathers, mirrors, etc.) can change the direction of the beam.


Lasers are a monochromatic (one color) concentrated beam of light. This means that when compared with a flashlight, the laser delivers more punch on a light detector. The alignment is more critical (as you’ll find out when you zig-zag a laser through several mirrors), so take your time and do these experiments in a steamy, dark bathroom after a hot shower. That way, you’ll be able to see the beam and align your optics easily.
[am4show have=’p8;p9;p99;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Are you ready to build your own laser theater? Here’s what you need:


  • Red laser pointer (NOT GREEN!)
  • 2-3 small mirrors (like mosaic mirrors)
  • Feather
  • 3 large paper clips
  • 10 brass fasteners
  • Index card
  • Cardboard
  • Rubber band or zip tie
  • Steamy dark bathroom room (like after a hot shower with the windows covered)
  • Two 3V DC motors
  • Two AA battery packs
  • Four AA batteries
  • Three alligator wires
  • Optional: plastic gem pieces


[/am4show]


Electric Eye

Wednesday February 3, 2010

This is a super-cool and ultra-simple circuit experiment that shows you how a CdS (cadmium sulfide cell) works. A CdS cell is a special kind of resistor called a photoresistor, which is sensitive to light.

A resistor limits the amount of current (electricity) that flows through it, and since this one is light-sensitive, it will allow different amounts of current through depends on how much light it "sees".

Photoresistors are very inexpensive light detectors, and you'll find them in cameras, street lights, clock radios, robotics, and more. We're going to play with one and find out how to detect light using a simple series circuit.

Materials:

  • AA battery case with batteries
  • one CdS cell
  • three alligator wires
  • LED (any color and type)

[am4show have='p8;p9;p20;p47;p108;p76;p89;p97;p99;' guest_error='Guest error message' user_error='User error message' ]

Download Student Worksheet & Exercises

Turn this into a super-cool burglar alarm!

Exercises

  1. How is a CdS cell like a switch? How is it not like a switch?
  2. When is the LED the brightest?
  3. How could you use this as a burglar alarm?

[/am4show]

This is a super-cool and ultra-simple circuit experiment that shows you how a CdS (cadmium sulfide cell) works. A CdS cell is a special kind of resistor called a photoresistor, which is sensitive to light.

A resistor limits the amount of current (electricity) that flows through it, and since this one is light-sensitive, it will allow different amounts of current through depends on how much light it "sees".

Photoresistors are very inexpensive light detectors, and you'll find them in cameras, street lights, clock radios, robotics, and more. We're going to play with one and find out how to detect light using a simple series circuit.

Materials:

  • AA battery case with batteries
  • one CdS cell
  • three alligator wires
  • LED (any color and type)

[am4show have='p8;p9;p20;p47;p108;p76;p89;p97;p99;' guest_error='Guest error message' user_error='User error message' ]

Download Student Worksheet & Exercises

Turn this into a super-cool burglar alarm!

Exercises

  1. How is a CdS cell like a switch? How is it not like a switch?
  2. When is the LED the brightest?
  3. How could you use this as a burglar alarm?

[/am4show]


Laser Burglar Alarm

Wednesday February 3, 2010

This is a beefier-version of the Electric Eye that will be able to turn on a buzzer instead of a LED by increasing the voltage in the circuit. This type of circuit is a light-actuated circuit. When a beam of light hits the sensor (the "eye"), a buzzer sounds. Use this to indicate when a door closes or drawer closes... your suspect will never know what got triggered.
[am4show have='p8;p9;p99;p108;' guest_error='Guest error message' user_error='User error message' ]
Materials:

  • Red laser (cheap dollar store kind works well)
  • 9V Battery
  • Three alligator clip leads
  • Buzzer (3-6V)
  • CdS Cell

Download Student Worksheet & Exercises

Exercises

  1. How is this circuit different from the Electric Eye experiment we did previously?
  2.  Name three other light sources that work to activate your circuit.

[/am4show]


Laser Door Alarm

Wednesday February 3, 2010

If you've already made the Laser Burglar Alarm (which is highly recommend doing FIRST), then you're probably wondering how to make the circuit act in the opposite way... meaning how do you make it so that the buzzer sounds when the light is turned off?

This circuit requires more patience and parts, but it's totally worth it. It uses the same parts as the previous experiment (plus a few more) with a couple of extra twists and turns in the circuit to let the buzzer know when it's time to turn off. Use this in doorways or as an invisible trip wire trigger across hallways.

Materials:

  • Red laser pointer
  • 9V battery or two AA's in a AA battery pack
  • 7 alligator clip leads
  • CdS Cell
  • 9V Battery OR 2 AA's in a battery holder
  • NPN Transistor 2N3904 or 2N222A
  • 4.7k-ohm resistor
  • Buzzer (3-6V)

[am4show have='p8;p9;p98;p99;p108;' guest_error='Guest error message' user_error='User error message' ]

Why bother with the transistor? The Electric Eye & the Burglar Alarm didn't have one! The reason you can't simply substitute a buzzer for the LED in the electric eye is that the buzzer draws much more current than the CdS cell supplies. We overcame this issue in the Burglar Alarm by increasing the voltage from 3V to 9V.  But how do you make the circuit detect darkness instead of light?

By using a transistor as a switch, we can make two circuits: one that triggers the transistor to turn on and off when we want it (when it sees dark, for example), and the other circuit to make the buzzer sound. We connect the two circuits by joining them together in such a way that the transistor switches the buzzer on when the CdS cell sees darkness. The transistor is our switch for the buzzer!

For younger kids, you might want to try making the trip wire alarm or the pressure sensor burglar alarm.

[/am4show]


Laser Light Show

Wednesday February 3, 2010

ss-laserWhat happens when you shine a laser beam onto a spinning mirror? In the Laser Maze experiment, the mirrors stayed put. What happens if you took one of those mirrors and moved it really fast?


It turns out that a slightly off-set spinning mirror will make the laser dot on the wall spin in a circle.  Or ellipse. Or oval.  And the more mirrors you add, the more spiro-graph-looking your projected laser dot gets.


Why does it work? This experiment works because of imperfections: the mirrors are mounted off-center, the motors wobble, the shafts do not spin true, and a hundred other reasons why our mechanics and optics are not dead-on straight.   And that’s exactly what we want – the wobbling mirrors and shaky motors make the pretty pictures on the wall!  If everything were absolutely perfectly aligned, all you would see is a dot.


Here’s how to do this experiment:


[am4show have=’p8;p9;p19;p46;p89;p99;p103;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Materials:


  • AA battery pack with AA batteries
  • two 1.5-3V DC motors OR rip them off old toys or personal fans sold in the summertime
  • keychain laser pointer
  • clothespin
  • two round mirrors (mosaic mirrors from the craft store work great)
  • two alligator clip leads
  • gear that fits onto the motor and has a flat side to attach to the mirror
  • 5-minute epoxy (don’t use hot glue – it’s not strong enough to hold the mirrors on at high motor speeds)

**Note – if this is your very first time wiring up an electrical circuit, I highly recommend doing this Easy Laser Light Show first. It uses a lot of the same parts, but it’s easier to build.**



Here’s what you do:


1. Insert the batteries into their case.


2. Use 5-minute epoxy to secure the gear onto the round mirror.


3. Press-fit the gear-mirror onto the shaft when the epoxy is dry.


4. Make the motor spin using the alligator clips and the battery case.


5. Turn down the lights and fire up the laser, aiming the beam onto the motor.


6. Shine the reflection somewhere easy to see, like the ceiling.


7. Once you’ve got this working, add a second mirror like you did in the laser maze.


[/am4show][am4show have=’p9;p46;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Advanced Two-Axis Laser Light Show

The second part of this experiment is for advanced students. What shapes can you make?  Is it tough to hold it all in place? Then here’s how to create a portable laser light show:


Materials:


  • Red laser pointer
  • 3VDC motors
  • 2 gears or corks (you’ll need a solid way to attach the mirror to the motor shaft tip)
  • two 1” round mirrors (use mosaic mirrors)
  • 2 DPDT switches with center off
  • 20 alligator clip leads  OR insulated wire if you already know how to solder
  • 2 AA battery packs with 4 AA’s
  • Two 1K potentiometers
  • Zip-tie (from the hardware store)
  • ½ ” or ¾ ” metal conduit hangers (size to fit your motors from the hardware store)
  • 3 sets of ¼ ” x 2″ bolts, nuts, and washers
  • 1 project container (at least 7” x 5”) with lid
  • Basic tools (scissors, hot glue gun, drill, wire strippers, pliers, screwdriver)

Click here to download the Schematic Wiring Diagram for the Advanced Laser Light Show.



Download Student Worksheet & Exercises


Exercises


  1. How does the mirror turn a laser dot into an image?
  2.  What happens when you add a second motor? Third?

[/am4show]


Space-Age Laser Communicator

Wednesday February 3, 2010

laser17This experiment is for advanced students.Did you know that when you talk inside a house, the windows vibrate very slightly from your voice? If you stand outside the house and aim a laser beam at the window, you can pick up the vibrations in the window and actually hear the conversation inside the house.


Remember how windows split a laser beam in two from the Laser Basics experiment? That’s the basic idea behind it. First, I’ll show you how to build your own space-age laser communicator, then you can work on your spy device.


The first thing we’re going to do is take the music from your stereo or MP3 player and transmit it on a laser beam to a detector on the other side. The detector has an earphone attached, so someone else can listen to the music from your laser. Weird, huh?


Here’s how to build your own:


[am4show have=’p9;p46;p107;p103;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Materials:



[/am4show]


Flashlight Laser Tag

Wednesday February 3, 2010

This super-cool project lets kids have the fun of playing tag in the dark on a warm summer evening, without the "gun" aspect traditionally found in laser tag. Kids not only get to enjoy the sport but also have the pride that they build the tag system themselves - something you simply can't get from opening up a laser tag game box.

While real laser tag games actually never use lasers, but rather infrared beams, this laser tag uses real lasers, so you'll want to arm the kids with the "no-lasers-on-the-face" with a 10-minute time-out penalty to ensure everyone has a good time. You can alternatively use flashlights instead of lasers, which makes the game a lot easier to tag someone out.

This game uses a simple two-transistor latching circuit design, so there's no programming or overly complicated circuitry to worry about. If you've never built this kind of circuit before, it's a perfect first step into the world of electronics.

I've provided you with three videos below. This first video is an introduction to what we are going to make and how it works. Here's what you need:

NOTE: We updated this circuit in 2023 to reflect "best practices" when using transistors. 

Be sure to build this project as shown in the schematic and breadboard diagrams, and not as shown in the video.

The material list below is based on the new design as shown in the schematic and breadboard diagrams on this page.

The videos show how to build the old circuit, but are still very useful.

[am4show have='p8;p9;p99;p103;' guest_error='Guest error message' user_error='User error message' ]
Materials (the list below builds one complete set per kid):

Materials (the list below builds one complete set per kid):

Flashlight Laser Tag Schematic:

Flashlight laser tag breadboard diagram:

Introduction to the Circuit

The next two videos below show you how to build the circuit, first on a breadboard, and then how to solder the circuit together, so you can opt to watch either one. If you have someone who's handy with tools and soldering irons, invite them to build this with you.

Building the Circuit on a Breadboard

Soldering the Circuit Together

You'll need one of these circuits for every player, although you can get by with one kid having a flashlight (this is the "it" person) and the other running around wearing the circuit trying not to get "tagged". You can mount these circuits inside a soapbox or cardboard box with the sensor and light peeking out. Add a belt or wrist strap and you're ready for action!

[/am4show]


Sunlight Alarm

Wednesday February 3, 2010

Wouldn't it be nice to wake up your brother or sister using an alarm you build yourself, triggered by natural sunlight? The happy news is now you can, using your Flashlight Laser Tag circuit you already built!

Since your circuit is already sensitive to light, you can transform it easily into an alarm clock that will buzz or light up when hit by the sun's rays.

Note - you can also use your Laser Door Alarm for this as well, since it's also triggered by light. However, the Burglar Alarm will not work, because it gets triggered by darkness, so unless you want your alarm to sound just as your drifting off to sleep, you'll want to use the Laser Door Alarm or the Flashlight Laser Tag circuit. Here's what you need to know (it's really simple...):

[am4show have='p8;p9;p99;p108;' guest_error='Guest error message' user_error='User error message' ]
Materials:


[/am4show]


Crystal Radio

Wednesday February 3, 2010

xtal3In addition to laser experiments, I thought you’d like to learn how to pick up sound that’s traveling on a light wave. A crystal radio is among the simplest of radio receivers – there’s no battery or power source, and nearly no moving parts. The source of power comes directly from the radio waves (which is a low-power, low frequency light wave) themselves.


The crystal radio turns the radio signal directly into a signal that the human ear can detect. Your crystal radio detects in the AM band that have been traveling from stations (transmitters) thousands of miles away. You’ve got all the basics for picking up AM radio stations using simple equipment from an electronics store. I’ll show you how…


The radio is made up of a tuning coil (magnet wire wrapped around a toilet paper tube), a detector (germanium diode) and crystal earphones, and an antenna wire.


One of the biggest challenges with detecting low-power radio waves is that there is no amplifier on the radio to boost the signal strength. You’ll soon figure out that you need to find the quietest spot in your house away from any transmitters (and loud noises) that might interfere with the reception when you build one of these.


One of things you’ll have is to figure out the best antenna length to produce the clearest, strongest radio signal in your crystal radio. I’m going to walk you through making three different crystal radio designs.


You’ll need to find these items below.


Here’s what you do:


[am4show have=’p8;p9;p84;p99;p103;’ guest_error=’Guest error message’ user_error=’User error message’ ]



[/am4show]


Squished Soda Can

Sunday January 31, 2010

An average can of soda at room temperature measures 55 psi before you ever crack it open. (In comparison, most car tires run on 35 psi, so that gives you an idea how much pressure there is inside the can!)


If you heat a can of soda, you’ll run the pressure over 80 psi before the can ruptures, soaking the interior of your house with its sugary contents. Still, you will have learned something worthwhile: adding energy (heat) to a system (can of soda) causes a pressure increase. It also causes a volume increase (kaboom!).
How about trying a safer variation of this experiment using water, an open can, and implosion instead of explosion?


Materials – An empty soda can, water, a pan, a bowl, tongs, and a grown-up assistant.


NOTE: If you can get a hold of one, use a beer can – they tend to work better for this experiment. But you can also do this with a regular old soda can. And no, I am not suggesting that kids should be drinking alcohol! Go ask a parent to find you one – and check the recycling bin.


[am4show have=’p8;p9;p93;p30;p57;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Prepare an ice bath by putting about ½” of ice water in a shallow dish. With an adult, place a few tablespoons of water in an empty soda or beer can and place the can upright in a skillet on the stove. When the can emits a think trickle of steam, grab the can with tongs and quickly invert it into the ice dish. CRACK!


Troubleshooting: The trick to making this work is that the can needs to be full of hot steam, which is why you only want to use a tablespoon or two of water in the bottom of the can. It’s alright if a bit of water is still at the bottom of the can when you flip it into the ice bath. In fact, there should be some water remaining or you’ll superheat the steam and eventually melt the can. You want enough water in the ice bath to completely submerge the top of the can.


Always use tongs when handling the heated can and make sure you completely submerge the top of the can in the icy water. The water needs to seal the hole in the top of the can so the steam doesn’t escape. Be prepared for a good, loud CRACK! when you get it right.


Why does this work? By heating up the water in the can, you’re changing the state of water from a liquid to a has (called water vapor), which drives out the air, leaving the steam inside. When inverted and cooled, the steam condenses to a small volume of liquid water (much smaller than if it was just hot air). The molecules in water vapor are a lot further apart than when they are in a liquid state. Since the air inside the can has been replaced by the steam, when it cools quickly, it creates a lower air pressure region in the can, so the air pressure surrounding the outside of the can rapidly crushes the can.


If you look really carefully as it condenses, you’ll see cold water from the bowl zoom into the can, just like when you suck water through a straw. The vacuum created int he can by the condensing steam creates a lower pressure, which pushes water into the can itself. When you suck from a straw, you’re creating a lower air pressure region in your mouth so that the surrounding air pressure pushes liquid up the straw to equalize the pressure.


Remember, high pressure always pushes!


[/am4show]


Bouncy Ball

Sunday January 10, 2010

This is one of those 'chemistry magic show' type of experiments to wow your friends and family. Here's the scoop: you take a cup of clear liquid, add it to another cup of clear liquid, stir for ten seconds, and you'll see a color change, a state change from liquid to solid, and you can pull a rubber-like bouncy ball right out of the cup.

If you have trouble locating the ingredients, you can order them online here:

  • Sodium Silicate (from Unit 3)
  • Ethyl Alcohol (check your pharmacy)
  • Disposable cups (at least two - and don't use your kitchen glassware, as you'll never get it clean again)
  • Popsicle sticks (again, use something disposable to stir with)



Download Student Worksheet & Exercises

1. In one cup, measure four tablespoons of sodium silicate solution (it should be a liquid). Sodium silicate can be irritating to the skin for some people, so wear rubber gloves when doing this experiment!

2. Measure 1 tablespoon of ethyl alcohol into a second cup. Ethyl alcohol is extremely flammable—cap it and keep out of reach when not in use.

3. Pour the alcohol into the sodium silicate solution and stir with a Popsicle stick.

4. You’ll see a color change (clear to milky-white) and a state change (liquid to a solid clump.

5. Using gloves, gather up the polymer ball and firmly squeeze it in your hands.

6. Compress it into the shape you want—is it a sphere, or do you prefer a dodecahedron?

7. Bounce it!

8. Be patient when squeezing the compound together. If it breaks apart and crumbles, gather up the pieces and firmly press together.

Store your bouncy ball in a Ziploc bag!

What’s Going On?

Silicones are water repellent, so you’ll find that food dye doesn’t color your bouncy ball. You’ll find silicone in greases, oils, hydraulic fluids, and electrical insulators.

The sodium silicate is a long polymer chain of alternating silicon and oxygen atoms. When ethanol (ethyl alcohol) is added, it bridges and connects the polymer chains together by cross-linking them.

Think of a rope ladder—the wooden rungs are the cross-linking agents (the ethanol) and the two ropes are the polymer chains (sodium silicate).

Safety information for Sodium Silicate: MSDS.

Questions to Ask

1. Before the reaction, what was the sodium silicate like? Was it a solid, liquid, or gas? What color was it? Was it slippery, grainy, viscous, etc.?

2. What was the ethanol like before the reaction?

3. How is the product (the bouncy ball) different from the two chemicals in the beginning?

4. Was the bouncy ball  the only molecule that was formed?

5.  Was this reaction a physical or chemical change?

Did you know? Silly putty is actually a mixture of silicone and chalk!


Glowing Slime

Sunday January 10, 2010

When you think of slime, do you imagine slugs, snails, and puppy kisses? Or does the science fiction film The Blob come to mind? Any way you picture it, slime is definitely slippery, slithery, and just plain icky — and a perfect forum for learning real science.


But which ingredients work in making a truly slimy concoction, and why do they work? Let’s take a closer look…


Imagine a plate of spaghetti. The noodles slide around and don’t clump together, just like the long chains of molecules (called polymers) that make up slime. They slide around without getting tangled up. The pasta by itself (fresh from the boiling water) doesn’t hold together until you put the sauce on. Slime works the same way. Long, spaghetti-like chains of molecules don’t clump together until you add the sauce … until you add something to cross-link the molecule strands together.


The sodium-tetraborate-and-water mixture is the “spaghetti” (the long chain of molecules, also known as a polymer), and the “sauce” is the glue-water mixture (the cross-linking agent). You need both in order to create a slime worthy of Hollywood filmmakers.


[am4show have=’p8;p9;p18;p45;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Materials:


  • popsicle sticks
  • water
  • disposable cups
  • borax (laundry whitener)
  • clear glue (or glue gel) or white glue
  • yellow highlighter
  • measuring spoons
  • scissors
  • UV black light


 
Download Student Worksheet & Exercises


To make this slime, combine ½ cup of water with 1 teaspoon of sodium tetraborate (also known as ‘Borax’) in a cup and stir with a popsicle stick.


In another cup, mix equal parts white glue and water. Add a glob of the glue mixture to the sodium tetraborate mixture. Stir for a second with a popsicle stick, then quickly pull the putty out of the cup and play with it until it dries enough to bounce on the table (3 to 5 minutes). Pick up an imprint from a textured surface or print from a newspaper, bounce and watch it stick, snap it apart quickly and ooze it apart slowly …


To make glowing slime, add one simple ingredient to make your slime glow under a UV light (or in sunlight)! You’ll need to extract the dye from the felt of a bright yellow highlighter pen and use the extract instead of water. (Simply cut open the pen and let water trickle over the felt into a cup: instant glow juice.) For the best slime results, substitute clear glue or glue gel for the white glue.


Don’t forget: You’ll need a long-wave UV source (also known as a “black light”) to make it glow (fluorescent lights tend to work better than incandescent bulbs or LEDs) – check the shopping list for where to get one. This slime will glow faintly in sunlight, because you get long-wave UV light from the sun — it’s just that you get all the other colors, too, making it hard to see the glow.


Is your slime a solid, a liquid, or a bubbly gas? The best slimes we’ve seen have all three states of matter simultaneously: solid chunks suspended in a liquidy form with gas bubbles trapped inside. Yeecccccch!!


What other stuff glows under a black light? Loads of stuff! There are a lot of everyday things that fluoresce (glow) when placed under a black light. Note that a black light emits high-energy UV light. You can’t see this part of the spectrum (just as you can’t see infrared light, found in the beam emitted from the remote control to the TV), which is why “black lights” were named that. Stuff glows because fluorescent objects absorb the UV light and then spit light back out almost instantaneously. Some of the energy gets lost during that process, which changes the wavelength of the light, which makes this light visible and causes the material to appear to glow. (More on this in Unit 9.)


How to Make Glow Juice

You can add glow juice in place of water in any experiment. Here’s how you make the glow juice by itself:



Moon Blob

moonblobThe most slippery substance on the planet, this dehydrated gel is a super-slippery, super long polymer chain of molecules that will actually climb up and out of your container if you don’t use a lid.  This slime is sensitive to light, temperature, and concentration (the amount of water you use) so if yours isn’t very responsive, check those three things.


Mixing this gel takes at least two days, and when you do it, make only a half recipe so you can make adjustments if yours isn’t quite right. We use ours on ‘Slip and Slides’ instead of water for a super-fun ride! (Hint – don’t try to stand, or you’ll break your arm when you crash!)


[/am4show]


What is Fire?

Sunday January 10, 2010

What state of matter is fire? Is it a liquid? I get that question a LOT, so let me clarify. The ancient scientists (Greek, Chinese… you name it) thought fire was a fundamental element. Earth, Air Water, and Fire (sometimes Space was added, and the Chinese actually omitted Air and substituted Wood and Metal instead) were thought to be the basic building blocks of everything, and named it an element. And it’s not a bad start, especially if you don’t have a microscope or access to the internet.


Today’s definition of an element comes from peeking inside the nucleus of an atom and counting up the protons. In a flame, there are lots of different molecules from NO, NO2, NO3, CO, CO2, O2, C… to name a few. So fire can’t be an element, because it’s made up of other elements. So, what is it?


[am4show have=’p8;p9;p18;p45;p91;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Fire is a combination of different gases and hot plasma. It’s a complicated exothermic (gives off heat) chemical reaction that releases a lot of heat and light (you can feel and see the flame). You need three things for a flame: oxygen, fuel, and a spark. When you take away one of these three, you snuff the flame and stop the chemical reaction. You start with fuel (usually contains carbon), and add oxygen to get carbon dioxide, carbon monoxide, nitric oxide, and many other gases and leftover ash. Most flames are hot enough to heat the gas mixture to create tiny bits of plasma within the flame, so fire is actually involved in two states of matter.


In this experiment, we’re going to see how you can protect a surface from burning using water. Are you ready?


Materials:


  • Shallow baking dish
  • Tongs
  • Rubbing Isopropyl Alcohol (50-91%)
  • Water (omit if using 50-70% alcohol)
  • Dollar bill
  • Fire extinguisher
  • Adult help


 
Download Student Worksheet & Exercises


What’s going on? Alcohol burns with a slightly blue and orange flame (as shown in the video). The secret to keeping the dollar bill from burning is the water you mixed in with the alcohol. Water has a high heat capacity, which means that the water absorbs the energy from the flame and keep the bill from catching on fire. If you dipped the dollar bill in pure 100% alcohol, the temperature would rise high enough on the bill to burn. The reason we chose a bill instead of regular paper is that the dollar bill is a combination of linen and paper, making it much stronger and absorbent for this experiment.


You need both the water and the alcohol for this experiment. The water, as it absorbs the energy from the flame, heats up to its boiling point and then vaporizes, keeping the bill cool enough to not catch on fire. The alcohol is the fuel needed to keep the flame going. It’s a delicate balance between the two, but here are a couple of variations you can try out:


  • You can change the color of the flame by adding in a sprinkling of salt (for yellow), boric acid (for green), or epsom salt (for white).
  • You can also try mixing different ratios of water to alcohol, using 50%, 70% and 91% isopropyl alcohol. You can also try ethyl alcohol (which is an entirely different molecule) but will react about the same with this experiment. Note that if you decrease the water content too much, you’re going to lose your dollar bill.

[/am4show]


Acids & Bases

Sunday January 10, 2010

If you had a choice between a glass of lemon juice or apple juice, most folks would pick the sweeter one – apple. Did you know that apples are loaded with malic acid, and are actually considered to be acidic? It’s just that there is so much more sugar in an apple than a lemon that your taste buds can be fooled. Here’s a scientific way (which is much more reliable) to tell how acidic something is.


Acids are sour tasting (like a lemon), bases are bitter (like unsweetened cocoa powder). Substances in the middle are more neutral, like water. Scientists use the pH (power of hydrogen, or potential hydrogen) scale to measure how acidic or basic something is. Hydrochloric acid registers at a 1, sodium hydroxide (drain cleaner) is a 14. Water is about a 7. pH levels tell you how acidic or alkaline (basic) something is, like dirt. If your soil is too acidic, your plants won’t attract enough hydrogen, and too alkaline attracts too many hydrogen ions. The right balance is usually somewhere in the middle (called ‘pH neutral’). Some plants change color depending on the level of acidity in the soil – hydrangeas turn pink in acidic soil and blue in alkaline soil.


There are many different kinds of acids: citric acid (in a lemon), tartaric acid (in white wine), malic acid (in apples), acetic acid (in vinegar), and phosphoric acid (in cola drinks). The battery acid in your car is a particularly nasty acid called sulfuric acid that will eat through your skin and bones. Hydrochloric acid is found in your stomach to help digest food, and nitric acid is used to make dyes in fabrics as well as fertilizer compounds.


[am4show have=’p8;p9;p18;p45;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Materials:


Here’s a video that shows you how to test several different things, including how to safely test stronger acids and bases, should you wish to test your own out.



Some things you can test (in addition to the ones in the video) include: Sprite, distilled white vinegar, baking soda, Vanish, laundry detergent, clear ammonia, powdered Draino, and Milk of Magnesia. DO NOT mix any of these together! Simply add a bit to each cup and test it with your pH strips. Here’s a quick video demonstration:


(Note – we didn’t list the chemicals on the shopping list as there were a LOT of stuff to get for only one experiment, so just sit back and watch!)



No pH strips? The chop up a head of red cabbage and whirl in a blender with water. Pass through a strainer (discard the solids), and pour this new ‘indicator’ into several cups. Add Sprite to one cup and watch for a color change. Add baking soda and watch for another color change. Continue down the line, adding only one chemical per cup into your cabbage juice.


Click here to view another version of this experiment: Chemical Matrix.


[/am4show]


Iodine Rainbow

Sunday January 10, 2010

This is the experiment that your audience will remember from your chemistry magic show. Here’s what happens – you call up six ‘helpers’ and hand each a seemingly empty test tube. Into each test tube, pour a little of the main gold-colored solution, say a few magic words, and their test tubes turn clear, black, pink, gold, yellow, and white. With a flourish, ask them to all pour their solutions back into yours and the final solution turns from inky black to clear. Voila!


I first saw a similar experiment when I was a kid, and I remembered it all the way through college, where I asked my professor how I could duplicate the experiment on my own. I was told that the chemicals used in that particular experiment were way too dangerous, and no substitute experiment was possible, especially for the color reversal at the end. I was determined to figure out an alternative. After two weeks of nothing but chemistry and experiment testing, I finally nailed it – and the best part is, you have most of these chemicals at the grocery store. (And the best part is, I can share it with you as I’ve eliminated the nasty chemicals so you don’t have to worry about losing an eyeball or a finger.)


NOTE: This experiment requires adult help, as it uses chemicals that are toxic if randomly mixed together.  Follow the instructions carefully, and do not mix random chemicals together.


Are you ready to mix up your own rainbow?


[am4show have=’p8;p9;p18;p45;p91;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Materials:


  • Iodine (non-clear, non-ammonia from the pharmacy)
  • Hydrogen peroxide (3% solution)
  • Vinegar (distilled white is best)
  • Cornstarch (tiny pinch) or one starch packing peanut
  • Water (distilled)
  • Sodium Thiosulfate
  • Sodium Carbonate (AKA: “washing soda“)
  • Phenolphthalein (keep this out of reach of kids) – this is optional
  • Disposable plastic cups (about eight)
  • Popsicle sticks
  • Gloves for your hands
  • Goggles for your face
  • Medicine droppers (at least four)


Download Student Worksheet & Exercises


[/am4show]


Dinosaur Toothpaste

Friday January 1, 2010

Hydrogen peroxide is used to fuel rockets, airplanes, and other vehicle engines. Chemistry teachers everywhere use it to demonstrate the power of a catalyst.

To speed up a reaction without altering the chemistry of the reaction involves adding a catalyst. A catalyst changes the rate of reaction but doesn’t get involved in the overall chemical changes.

For example, leaving a bottle of hydrogen peroxide outside in the sunlight will cause the hydrogen peroxide to decompose. However, this process takes a long time, and if you don’t want to wait, you can simply toss in a lump of charcoal to speed things along.

The carbon is a catalyst in the reaction, and the overall effect is that instead of taking two months to generate a balloon full of oxygen, it now only takes five minutes. The amount of charcoal you have at the end of the reaction is exactly the same as before it started.

A catalyst can also slow down a reaction. A catalytic promoter increases the activity, and a catalytic poison (also known as a negative catalyst, or inhibitor) decreases the activity of a reaction. Catalysts offer a different way for the reactants to become products, and sometimes this means the catalyst reacts during the chemical reaction to form intermediates. Since the catalyst is completely regenerated before the reaction is finished, it’s considered ‘not used’ in the overall reaction.

In this experiment, you'll see that there's a lot of oxygen hiding inside the peroxide - enough to really make things interesting and move around! You'll also find out what happens to soap when you bubble oxygen through it. Are you ready?

[am4show have='p8;p9;p101;' guest_error='Guest error message' user_error='User error message' ]
Materials:

  • hydrogen peroxide
  • yeast (the kind you'd use for baking bread)
  • liquid soap
  • shallow dish
  • water or soda bottle

The hydrogen is mixed with the soap first. The catalyst (yeast) causes the hydrogen peroxide to break down into oxygen and water. Since there's a lot of oxygen trapped in the peroxide, this decomposition happens very quickly and the oxygen rushes out of the container fast! As this happens, the water and soap mix together and turns into foam as the oxygen bubbles through trying to escape.

[/am4show]

 


Slingshot Rocket

Friday January 1, 2010

This project is simple, yet highly satisfying.  The current record distance traveled is 74 feet... can you beat that?  Make sure you launch these UP, not horizontally! You only need three items, all of which are in your house right now! First, you need a piece of...

[am4show have='p8;p9;p10;p37;p109;p93;p95;' guest_error='Guest error message' user_error='User error message' ]

...paper, a skinny rubber band, and a pair of scissors.


[/am4show]

This project is simple, yet highly satisfying.  The current record distance traveled is 74 feet... can you beat that?  Make sure you launch these UP, not horizontally! You only need three items, all of which are in your house right now! First, you need a piece of...

[am4show have='p8;p9;p10;p37;p109;p93;p95;' guest_error='Guest error message' user_error='User error message' ]

...paper, a skinny rubber band, and a pair of scissors.


[/am4show]


Bomber Plane & Wind Tunnel

Friday January 1, 2010
When designing airplanes, engineers pay attention to details, such as the position of two important points: the center of gravity and the center of pressure (also called the center of lift). On an airplane, if the center of gravity and center of pressure points are reversed, the aircraft’s flight is unstable and it will somersault into chaos. The same is true for rockets and missiles!

Let’s find the center of gravity on your airplane. Grab your flying machine and sharpened pencil. You can find the ‘center of gravity’ by balancing your airplane on the tip of a pencil. Label this point “CG” for Center of Gravity.

Materials:

  • sheet of paper

  • hair dryer

  • pencil with a sharp tip


We're going to make a paper airplane first, and then do a couple of wind tunnel tests on it.

For the project, all you need is a sheet of paper and five minutes... this is one my favorite fliers that we make with our students!


Find the Center of Pressure (CP) by doing the opposite: Using a blow-dryer set to low-heat so you don’t scorch your airplane, blast a jet of air up toward the ceiling. Put your airplane in the air jet and, using a pencil tip on the top side of your plane, find the point at which the airplane balances while in the airstream. Label this point “CP” for Center of Pressure. (Which one is closest to the nose?)


Besides paying attention to the CG and CP points, aeronautical engineers need to figure out the static and dynamic stability of an airplane, which is a complicated way of determining whether it will fly straight or oscillate out of control during flight. Think of a real airplane and pretend you’ve got one balanced on your finger. Where does it balance? Airplanes typically balance around the wings (the CG point). Ever wonder why the engines are at the front of small airplanes? The engine is the heaviest part of the plane, and engineers use this weight for balance, because the tail (elevator) is actually an upside-down wing that pushes the tail section down during flight.

Dart Flyer

Friday January 1, 2010
How does an airplane remain stable during flight? Positive stability means that the airplane is designed so that if the pilot jams on the controls during straight and level flight (in other words, pitch up hard), and then let go, the airplane will more or less return to straight and level flight.

Let's make another favorite flyer of mine...
[am4show have='p8;p9;p93;' guest_error='Guest error message' user_error='User error message' ]



Here’s how stability works: When the airplane’s nose suddenly pitches up, the wind speed over the wings slows and decreases the lift on the plane. This causes the nose to tip downwards and the wind to rush over the wings again, creating more lift. This cycle eventually dampens out and soon the airplane is flying level again.

If, however, you have a negative stability (meaning that your CG is aft of or behind the CP), when the airplane suddenly pitches up, one of several things may happen, all of which require sick bags and a parachute. One of the worst cycles is this: When a tail-heavy plane noses down, the speed over the wings increases and provides more lift but only briefly, because a tail-heavy plane will keep its nose up until the wind speed slows so much that the winds stall. Lift is no longer generated by wind flowing over the wings, because there is no wind, and the airplane “falls” a distance until the air flows back over the wings. This generates a lot of lift very quickly until the tail section tilts the nose back up. The cycle continues to worsen each time with greater “fall” distances” that place huge structural forces on the fuselage or body of the plane until you jump ship.

Can you find both the center of pressure AND the center of gravity? Does it matter which one is closer to the nose for stable flight? (Hint... yes, it does!) Here are directions for how to make an easy wind tunnel to test your airplanes.

[/am4show]

Flying Contraptions

Friday January 1, 2010

Mathematically speaking, this particular flying object shouldn't be able to fly.  What do you think about that?

Why can this thing fly? It doesn’t even LOOK like a plane! When I teach at the university, this is the plane that mathematically isn’t supposed to be able to fly! There are endless variations to this project—you can change the number of loops and the size of loops, you can tape two of these together, or you can make a whole pyramid of them. Just be sure to have fun!

Find the Center of Pressure (CP) by doing the opposite: Using a blow-dryer set to low-heat so you don’t scorch your airplane, blast a jet of air up toward the ceiling. Put your airplane in the air jet and, using a pencil tip on the top side of your plane, find the point at which the airplane balances while in the airstream. Label this point “CP” for Center of Pressure. (Which one is closest to the nose?)

Besides paying attention to the CG and CP points, aeronautical engineers need to figure out the static and dynamic stability of an airplane, which is a complicated way of determining whether it will fly straight or oscillate out of control during flight. Think of a real airplane and pretend you’ve got one balanced on your finger. Where does it balance? Airplanes typically balance around the wings (the CG point). Ever wonder why the engines are at the front of small airplanes? The engine is the heaviest part of the plane, and engineers use this weight for balance, because the tail (elevator) is actually an upside-down wing that pushes the tail section down during flight.

When we use math to add up the forces (the pull of gravity would be the weight, for example), it works out that there isn’t enough lift generated by thrust to overcome the weight and drag. When I say, “mathematically speaking...” I mean that the numbers don’t work out quite right. When this happens in science for real scientists, it usually means that they don’t fully understand something yet. There are a number of ‘unsolved’ mysteries still in science.. maybe you’ll be able to help us figure them out?

[am4show have='p8;p9;p93;' guest_error='Guest error message' user_error='User error message' ]
[/am4show]


Pop Rockets

Friday January 1, 2010

Rockets shoot skyward with massive amounts of thrust, produced by chemical reaction or air pressure. Scientists create the thrust force by shoving a lot of gas (either air itself, or the gas left over from the combustion of a propellant) out small exit nozzles.

According to the universal laws of motion, for every action, there is equal and opposite reaction. If flames shoot out of the rocket downwards, the rocket itself will soar upwards. It’s the same thing if you blow up a balloon and let it go—the air inside the balloon goes to the left, and the balloon zips off to the right (at least, initially, until the balloon neck turns into a thrust-vectored nozzle, but don’t be concerned about that just now).

A rocket has a few parts different from an airplane. One of the main differences is the absence of wings. Rockets utilize fins, which help steer the rocket, while airplanes use wings to generate lift. Rocket fins are more like the rudder of an airplane than the wings.

Another difference is the how rockets get their speed. Airplanes generate thrust from a rotating blade, whereas rockets get their movement by squeezing down a high-energy gaseous flow and squeezing it out a tiny exit hole.

If you’ve ever used a garden hose, you already know how to make the water stream out faster by placing your thumb over the end of the hose. You’re decreasing the amount of area the water has to exit the hose, but there’s still the same amount of water flowing out, so the water compensates by increasing its velocity. This is the secret to converging rocket nozzles—squeeze the flow down and out a small exit hole to increase velocity.

There comes a point, however, when you can’t get any more speed out of the gas, no matter how much you squeeze it down. This is called “choking” the flow. When you get to this point, the gas is traveling at the speed of sound (around 700 mph, or Mach 1). Scientists found that if they gradually un-squeeze the flow in this choked state, the flow speed actually continues to increase. This is how we get rockets to move at supersonic speeds or above Mach 1.

f18The image shown here is a real picture of an aircraft as it breaks the sound barrier. This aircraft is passing the speed at which sounds travel. The white cloud you see in the photo is related to the shock waves that are forming around the craft as it moves into supersonic speeds. Because the aircraft is moving through air, which is a gas, the gas can compress and results in a shock wave.

You can think of a shock wave as big pressure front. In this photo, the pressure is condensing water vapor in the air, hence the cloud. There are lots of things on earth that break the sound barrier – bullets and bullwhips, for example. The loud crack from a whip is the tip zipping faster than the speed of sound.

The rockets we're about to build get their thrust by generating enough pressure and releasing that pressure very quickly. You will generate pressure both by pumping and by chemical reaction, which generates gaseous products. Let's get started!

For this experiment, you will need:

[am4show have='p8;p9;p10;p37;p109;p95;' guest_error='Guest error message' user_error='User error message' ]

  • film canister or other plastic container with a tight-fitting lid (like a mini-M&M container)
  • alka-seltzer or generic effervescent tablets
  • water
  • outside area for launching

The record for these rockets is 28' high. What do you think about that? Note - you can use anything that uses a chemical reaction... what about baking soda and vinegar? Baking powder? Lemon juice?


Important question: Does more water, tablets, or air space give you a higher flight?

Variations: Add foam fins and a foam nose (try a hobby or craft shop), hot glued into place. Foam doesn’t mind getting wet, but paper does. Put the fins on at an angle and watch the seltzer rocket spin as it flies skyward. You can also tip the rocket on its side and add wheels for a rocket car, stack rockets, for a multi-staging project, or strap three rockets together with tape and launch them at the same time! You can also try different containers using corks instead of lids.


More Variations: What other chemicals do you have around that also produces a gas during the chemical reaction? Chalk and vinegar, baking soda, baking powder, hydrogen peroxide, isopropyl alcohol, lemon juice, orange juice, and so on.

[/am4show]

[am4show have='p9;p39;' guest_error='Guest error message' user_error='User error message' ]

Advanced students: Download your Pop Rockets Lab here.

[/am4show]


Star & Planet Trails

Sunday December 13, 2009

These are a set of videos made using planetarium software to help you see how the stars and planets move over the course of months and years. See what you think and tell us what you learned by writing your comments in the box below.


What’s odd about these star trails?

You can really feel the Earth rolling around under you as you watch these crazy star trails.
[am4show have=’p8;p9;p17;p44;p105;p67;’ guest_error=’Guest error message’ user_error=’User error message’ ]



 
Download Student Worksheet & Exercises


Do the planets follow the same arc across the night sky? You bet! All eight planets follow along the same arc that the sun follows, called the ecliptic. Here’s how the planets move across the sky:



Exercises:


  1. If you have constellations on your class ceiling, chart them on a separate page marking the positions of the rocks with X’s.
  2. Tonight, find two constellations that you will chart. Bring them with you tomorrow using the technique outlined above in Experiment.

[/am4show]


Build a REAL Scale Model of the Solar System

Sunday December 13, 2009

Ever wonder exactly how far away the planets really are?  Here’s the reason they usually don’t how the planets and their orbits to scale – they would need a sheet of paper nearly a mile long!


To really get the hang of how big and far away celestial objects really are, find a long stretch of road that you can mark off with chalk.  We’ve provided approximate (average) orbital distances and sizes for building your own scale model of the solar system.


When building this model, start by marking off the location of the sun (you can use chalk or place the objects we have suggested below as placeholders for the locations).  Are you ready to find out what’s out there?  Then let’s get started.


Materials:


  • measuring tape (the biggest one you have)
  • tape or chalk to mark off the locations
  • 2 grains of sand or white sugar
  • 12″ beach ball
  • 3 peppercorns
  • golf or ping pong ball
  • shooter-size marble
  • 2 regular-size marbles

[am4show have=’p8;p9;p17;p44;p96;p73;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Download Student Worksheet & Exercises


All distances are measured from the center of the sun. (In some cases, you might just want to use the odometer in your car to help you measure the distance!


Sun (12″ beach ball) at the starting point.


Mercury (grain of sand) is 41 feet from the sun.


Venus (single peppercorn) is 77 feet from the sun.


Earth (single peppercorn) is 107 feet from the sun.


Mars (half a peppercorn) is 163 feet from the sun.


Jupiter (golf or ping pong ball) is 559 feet from the sun.


Saturn (shooter-size marble) is 1,025 feet from the sun.


Uranus (regular-size marble) is 2,062 feet from the sun.


Neptune (regular marble) is 3,232 feet from the sun.


Pluto (grain of sand) is 4,248 feet from the sun.


Nearest Star (Alpha Centauri) is 5500 miles from the sun.


Is Your Solar System Too Big?

If these distances are too large for you, simply shrink all objects to the size of the period at the end of this sentence and you’ll get your solar system to fit inside your house using these measurements below.


First, draw a tiny dot for the Sun.  The diameter of the sun for this scale model is 0.1″, but we’re going to ignore this and all other planet diameters so we can fit this model within a 35′ scale.


We’re going to ignore the sizes of the planets and just focus on how far apart everything is. All distances listed below are measured from the sun.  Start by marking off the position of the sun with the tip of a sharp pencil.


Here are the rest of the distances you need to mark off:


Mercury is 4 inches from the sun.


Venus is 7.75 inches from the sun.


Earth is 10 inches from the sun.


Mars is 1′ 4″ from the sun.


Jupiter is 4′ 8″ from the sun.


Saturn is 8′ 6.5″ from the sun.


Uranus is 17′ 2″ from the sun.


Neptune is 26′ 11″ from the sun.


Pluto is 35′ 5″ from the sun.


Our nearest star, Alpha Centauri, is approximately 46 miles from the sun.


Did You Notice…?

Are you mind-boggled yet? Did you notice how the solar system is really just ’empty space’? Our models shown here are too small to start bringing in the moons, but you can see why posters showing the planets are not drawn to scale.  What are your thoughts on this experiment? Tell us in the comment area below!


For Advanced Students:

[/am4show][am4show have=’p9;p44;’ guest_error=’Guest error message’ user_error=’User error message’ ]


If you really want to play with the different distances on your own, use this orbital calculator online to help convert the distances for you.


[/am4show]


Solar System Treasure Hunt

Sunday December 13, 2009

After you've participated in the Planetarium Star Show (either live or by listening to the MP3 download), treat your kids to a Solar System Treasure Hunt!  You'll need some sort of treasure (I recommend astronomy books or a pair of my favorite binoculars, but you can also use 'Mars' candy bars or home made chocolate chip cookies (call them Galaxy Clusters) instead.

You can print out the clues and hide these around your house on a rainy day.  Did you know that I made these clues up myself as a refresher course after the astronomy presentation?  Enjoy!

[am4show have='p8;p9;p17;p44;p73;' guest_error='Guest error message' user_error='User error message' ]
Astronomy Clues
Click here to download the PDF version or the Word DOC version.


Download Student Worksheet & Exercises

You can print out images of each planet and match them up with the clues indicated below.  Post images of each of the planets along with the clue for the next one to really make this an out-of-this-world experience!

The Sun (CLUE #1): Hand this one to the kids to get started.

This object is hot, but not on fire.
Explore the dryer but don’t perspire!

Mercury (CLUE #2): Hide this clue below in the dryer.

This planet is closest, but not the hottest.
Check the sock drawer, and don’t be modest!

Venus (CLUE #3): Hide this clue below in the sock drawer.

This planet is so hot it can melt a cannonball,
Crush spaceships, rain acid, and is in tree tall.

Earth (CLUE #4): Hide this clue below in a tree (or plant).

Most of this planet is covered with water.
Visit the bathtub without making it hotter.

Mars (CLUE #5): Hide this clue below in the bathtub.

This planet is basically a rusty burp.
Discover the refrigerator and take a slurp.

Jupiter (CLUE #6): Hide this clue below next to the milk.

A planet so large it can hold the rest,
Explore our library with infinite zest!

Saturn (CLUE #7): Hide this clue below with a stack of books.

This planet had rings, but not made of gold.
Explore near the front door like an astronaut bold!

Uranus (CLUE #8): Hide this clue below on the front door.

Smacked so hard it now rolls on its side,
Find the window that is ever so wide.

Neptune (CLUE #9): Hide this clue below by sticking it on a window.

Check the sink for hurricane,
gigantic blue farts, and diamond rain.

Pluto (CLUE #10): Hide this clue below near the sink with the TREASURE!

Instead of one there were two, then four…
Visit the mailbox for the one that is no more.

[/am4show]


How to View the Sun Safely

Sunday December 13, 2009

You know you're not supposed to look at the sun, so how can you study it safely?  I'm going to show you how to observe the sun safely using a very inexpensive filter.  I actually keep one of these in the glove box of my car so I can keep track of certain interesting sunspots during the week!

The visible surface of the sun is called the photosphere, and is made mostly of plasma (remember the grape experiment?) that bubbles up hot and cold regions of gas. When an area cools down, it becomes darker (called sunspots). Solar flares (massive explosions on the surface), sunspots, and loops are all related the sun’s magnetic field. While scientists are still trying to figure this stuff out, here’s the latest of what they do know...

The sun is a large ball of really hot gas - which means there are lots of naked charged particles zipping around. And the sun also rotates, but the poles and the equator move and different speeds (don’t forget – it’s not a solid ball but more like a cloud of gas). When charged particles move, they make magnetic fields (that’s one of the basic laws of physics). And the different rotation rates allow the magnetic fields to ‘wind up’ and cause massive magnetic loops to eject from the surface, growing stronger and stronger until they wind up flipping the north and south poles of the sun (called ‘solar maximum’). The poles flip every eleven years.

There have been several satellites specially created to observe the sun, including Ulysses (launched 1990, studied solar wind and magnetic fields at the poles), Yohkoh (1991-2001, studied x-rays and gamma radiation from solar flares), SOHO (launched 1995, studies interior and surface), and TRACE (launched 1998, studies the corona and magnetic field).

Ok - so back to observing the sun form your own house. Here's what you need to do:

[am4show have='p8;p9;p17;p44;p105;' guest_error='Guest error message' user_error='User error message' ]
Materials:

  • Baader filter film
  • set of eyeballs


Click here for an inexpensive Baader filter film. You can use these with your naked eye or over the OPEN END (not the eyepeice) of a telescope.  See image below:

 

Want to see a BIG solar flare?
[/am4show]


Satellite Crash!

Sunday December 13, 2009

The Hubble Space Telescope (HST) zooms around the Earth once every 90 minutes (about 5 miles per second), and in August 2008, Hubble completed 100,000 orbits! Although the HST was not the first space telescope, is the one of the largest and most publicized scientific instrument around. Hubble is a collaboration project between NASA and the ESA (European Space Agency), and is one of NASA’s “Great Observatories” (others include Compton Gamma Ray Observatory, Chandra X-Ray Observatory, and Spitzer Space Telescope). Anyone can apply for time on the telescope (you do not need to be affiliated with any academic institution or company), but it’s a tight squeeze to get on the schedule.

Hubble’s orbit zooms high in the upper atmosphere to steer clear of the obscuring haze of molecules in the sea of air. Hubble’s orbit slowly decays over time and begins to spiral back into Earth until the astronauts bump it back up into a higher orbit.

But how does a satellite stay in orbit? Try this experiment now:

Materials:

  • marble
  • paper
  • tape

[am4show have=’p8;p9;p17;p44;p109;p96;’ guest_error=’Guest error message’ user_error=’User error message’ ]

 
Download Student Worksheet & Exercises

Troubleshooting: Expect to find marbles flying everywhere with this experiment! This quick activity demonstrates the idea of centripetal (centrifugal) acceleration. What happens when you circle the cone too slow or too fast? The marble itself is the satellite (like HST), and the cone’s apex (tip) is the Earth. When the marble zooms around too slow, it falls back into the Earth. So what keeps it up in “orbit”?

The faster an object moves, the greater the acceleration against the force of gravity (toward the Earth in this case). Think back to the Physics lab – when a marble went too slow through the roller coaster loop, it crashed back to the floor. When it went too fast, it flew off the track. There was a certain speed that was needed for the marble to stay in the loop and on course. The same is true for satellites in outer space.

If you have trouble with this experiment, just replace the paper cone with a disposable cup with a lid and try again (with the lid in place), and see if you can keep the marble circling around the top rim.

Exercises

  1.  What happens when your marble satellite moves too slowly?
  2.  What happens when the marble satellite orbits too fast?
  3. What effect does changing the marble mass have on your satellite speed?
  4.  How is this model like the real thing?

[/am4show]

Air Horns & Sonic BOOM!

Sunday November 29, 2009

f18Sound can change according to the speed at which it travels. Another word for sound speed is pitch. When the sound speed slows, the pitch lowers. With clarinet reeds, it’s high. Guitar strings can do both, as they are adjustable. If you look carefully, you can actually see the low pitch strings vibrate back and forth, but the high pitch strings move so quickly it’s hard to see. But you can detect the effects of both with your ears.

[am4show have=’p8;p9;p16;p43;p64;p100;’ guest_error=’Guest error message’ user_error=’User error message’ ]

The range of your ears is about 20 – 20,000 Hz (cycles per second). Bats and dogs can hear a lot higher than we can. The image (right) is a real picture of an aircraft as it breaks the sound barrier – meaning that the aircraft is passing the speed that sounds travels at (about 700 mph). The white cloud you see in the photo is related to the shock waves that are forming around the craft as it moves into supersonic speeds. You can think of a shock wave as big pressure front, which creates clouds. In this photo, the pressure from the shock waves is condensing the water vapor in the air.

There are lots of things on earth that break the sound barrier – bullets and bullwhips, for example. The loud crack from a whip is the tip zipping faster than the speed of sound.

shockwaveSo why do we hear a boom at all? Sonic booms are created by air pressure (think of how the water collects at the bow of a boat as it travels through the water). The vehicle pushes air molecules aside in such a way they are compressed to the point where shock waves are formed. These shock waves form two cones, at the nose and tail of the plane. The shock waves move outward and rearward in all directions and usually extend to the ground.

As the shock cones spread across the landscape along the flightpath, they create a continuous sonic boom. The sharp release of pressure, after the buildup by the shock wave, is heard as the sonic boom.

How to Make an Air Horn

Let’s learn how to make loud sonic waves… by making an air horn. Your air horn is a loud example of how sound waves travel through the air. To make an air horn, poke a hole large enough to insert a straw into the bottom end of a black Kodak film canister. (We used the pointy tip of a wooden skewer, but a drill can work also.) Before you insert the straw, poke a second hole in the side of the canister, about halfway up the side.

Here’s what you need:

  • 7-9″ balloon
  • straw
  • film canister
  • drill and drill bits

Grab an un-inflated balloon and place it on your table. See how there are two layers of rubber (the top surface and the bottom surface)? Cut the neck off a balloon and slice it along one of the folded edges (still un-inflated!) so that it now lays in a flat, rubber sheet on your table.

Drape the balloon sheet over the open end of the film canister and snap the lid on top, making sure there’s a good seal (meaning that the balloon is stretched over the entire opening – no gaps). Insert the straw through the bottom end, and blow through the middle hole (in the side of the canister).

You’ll need to play with this a bit to get it right, but it’s worth it! The straw needs to *just* touch the balloon surface inside the canister and at the right angle, so take a deep breath and gently wiggle the straw around until you get a BIG sound. If you’re good enough, you should be able to get two or three harmonics!

 

Download Student Worksheet & Exercises

Troubleshooting: Instead of a rubber band vibrating to make sound, a rubber sheet (in the form of a cut-up balloon) vibrates, and the vibration (sound) shoots out the straw. This is one of the pickiest experiments – meaning that it will take practice for your child to make a sound using this device. The straw needs to barely touch the inside surface of the balloon at just the right angle in order for the balloon to vibrate. Make sure you’re blowing through the hole in the side, not through the straw (although you will be able to make sounds out of both attempts).

Here’s a quick video where you can hear the small sonic boom from a bull whip:

Since most of us don’t have bull whips, might I recommend a twisted wet towel? Just be sure to practice on a fence post, NOT a person!

Exercises 

  1. Why do we use a straw with this experiment?
  2. Does the length of the straw matter? What will affect the pitch of this instrument?

[/am4show]

The Best Parent-Annoyer Ever

Sunday November 29, 2009

This is one of my absolute favorites, because it’s so unexpected and unusual… the setup looks quite harmless, but it makes a sound worse than scratching your nails on a chalkboard. If you can’t find the weird ingredient, just use water and you’ll get nearly the same result (it just takes more practice to get it right). Ready?

NOTE: DO NOT place these anywhere near your ear… keep them straight out in front of you.

[am4show have=’p8;p9;p16;p43;p64;p100;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Here’s what you need:

  • water or violin rosin
  • string
  • disposable plastic cup
  • pokey-thing to make a hole in the cup

 
Download Student Worksheet & Exercises

Exercises

  1. What does the rosin (or water) do in this experiment?
  2. What is vibrating in this experiment?
  3. What is the cup for?

[/am4show]

Humming Balloon

Sunday November 29, 2009

You can easily make a humming (or screaming!) balloon by inserting a small hexnut into a balloon and inflating. You can also try pennies, washers, and anything else you have that is small and semi-round. We have scads of these things at birthday time, hiding small change in some and nuts in the others so the kids pop them to get their treasures. Some kids will figure out a way to test which balloons are which without popping… which is what we’re going to do right now.

[am4show have=’p8;p9;p16;p43;p64;p100;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Here’s what you need:

  • hexnut
  • balloon
  • your lungs

 
Download Student Worksheet & Exercises

What to do: Place a hexnut OR a small coin in a large balloon. Inflate the balloon and tie it. Swirl the balloon rapidly to cause the hexnut or coin to roll inside the balloon. The coin will roll for a very long time on the smooth balloon surface. At high coin speeds, the frequency with which the coin circles the balloon may resonate with one of the balloon’s “natural frequencies,” and the balloon may hum loudly.

Exercises

  1. How does sound travel?
  2. What is pitch?
  3. How is frequency related to pitch?

[/am4show]

How a Record Player Works

Sunday November 29, 2009

Before CDs, there were these big black discs called records. Spinning between 33 and 45 times per minute on a turntable, people used to listened to music just like this for nearly a century. Edison, who had trouble hearing, used to bite down hard on the side of his wooden record player (called a phonograph) and “hear” the music as it vibrated his jaw.

Many people today still think that records still sound better than CDs (I think they do), especially if the record is well cared for and their players are tuned just right. Here’s a video on how a record works:

[am4show have=’p8;p9;p16;p43;p100;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Here’s what you need:

  • an old turntable (do you have one in your garage?)
  • old record that can be scratched
  • tack
  • plastic container, like a clean yogurt or butter tub

If you have an old turntable and OLD record that can be scratched, here’s how to listen to the music without using regular speakers!

[/am4show]

Potato Cannon

Saturday November 7, 2009

This experiment is for Advanced Students.There are several different ways of throwing objects. This is the only potato cannon we’ve found that does NOT use explosives, so you can be assured your kid will still have their face attached at the end of the day. (We’ll do more when we get to chemistry, so don’t worry!)

These nifty devices give off a satisfying *POP!!* when they fire and your backyard will look like an invasion of aliens from the French Fry planet when you’re done. Have your kids use a set of goggles and do all your experimenting outside.

Here’s what you need:

[am4show have=’p9;p42;p88;p92;p103;’ guest_error=’Guest error message’ user_error=’User error message’ ]

  • potatoes
  • an acrylic tube (clear is best so you can see what’s happening inside!)
  • wooden dowel
  • washer (this is your ‘hand-saver’)

Where is the potential energy the greatest? How much energy did your spud have at this point? Hmmm… let’s see if we can get a few actual numbers with this experiment. In order to calculate potential energy at the highest point of travel, you’ll need to figure out how high it went.

Here are instructions for making your own height-gauge:

Once you get your height gauge working right, you’ll need to track your data. Start a log sheet in your journal and jot down the height for each launch. Let’s practice a sample calculation:

If you measured an angle of 30 degrees, and your spud landed 20 feet away, we can assume that the spud when highest right in the middle of its flight, which is halfway (10 feet). Use basic trigonometry to find the height 45 degrees up at a horizontal distance ten feet away to get:

height = h = (10′) * (tan 30) = 5.8 feet
(Convert this to meters by: (5.8 feet) * (12 inches/foot) / (39.97 inches/meter) = 1.8 meters)

I measured the mass of my spud to be 25 grams (which is 0.025 kg).

Now, let’s calculate the potential energy:

PE = mgh = (0.025 kg) * (1.8 meters) * (10 m/s2) = 0.44 Joules

How fast was the spud going before it smacked into the ground? Set PE = KE to solve for velocity:

mgh = 0.5 mv2 gives v = (2gh)1/2

Plug in your numbers to get:

v = [(2) * (10) * (1.8)]2 = 6 m/s (or about 20 feet per second). Cool!

[/am4show]

Bobsleds

Saturday November 7, 2009

Bobsleds use the low-friction surface of ice to coast downhill at ridiculous speeds. You start at the top of a high hill (with loads of potential energy) then slide down a icy hill til you transform all that potential energy into kinetic energy.  It’s one of the most efficient ways of energy transformation on planet Earth. Ready to give it a try?

This is one of those quick-yet-highly-satisfying activities which utilizes ordinary materials and turns it into something highly unusual… for example, taking aluminum foil and marbles and making it into a racecar.

While you can make a tube out of gift wrap tubes, it’s much more fun to use clear plastic tubes (such as the ones that protect the long overhead fluorescent lights). Find the longest ones you can at your local hardware store. In a pinch, you can slit the gift wrap tubes in half lengthwise and tape either the lengths together for a longer run or side-by-side for multiple tracks for races. (Poke a skewer through the rolls horizontally to make a quick-release gate.)

Here’s what you need:

  • aluminum foil
  • marbles (at least four the same size)
  • long tube (gift wrapping tube or the clear protective tube that covers fluorescent lighting is great)

[am4show have=’p8;p9;p15;p42;p75;p85;p88;p92;p100;’ guest_error=’Guest error message’ user_error=’User error message’ ]

bobsledsIf you’re finding that the marbles fall out before the bobsled reaches the bottom of the slide, you need to either crimp the foil more closely around the marbles or decrease your hill height.

Check to be sure the marbles are free to turn in their “slots” before launching into the tube – if you’ve crimped them in too tightly, they won’t move at all. If you oil the bearings with a little olive oil or machine oil, your tube will also get covered with oil and later become sticky and grimy… but they sure go faster those first few times!

 
Download Student Worksheet & Exercises

Exercises Answer the questions below:

  1. Potential energy is energy that is related to:
    1. Equilibrium
    2. Kinetic energy
    3. Its system
    4. Its elevation
  2. If an object’s energy is mostly being used to keep that object in motion, we can say it has what type of energy?
    1. Kinetic energy
    2. Potential energy
    3. Heat energy
    4. Radiation energy
  3. True or False: Energy is able to remain in one form that is usable over and over again.
    1. True
    2. False

[/am4show]

Roller Coasters

Saturday November 7, 2009

We're going to build monster roller coasters in your house using just a couple of simple materials. You might have heard how energy cannot be created or destroyed, but it can be transferred or transformed (if you haven't that's okay - you'll pick it up while doing this activity).

Roller coasters are a prime example of energy transfer: You start at the top of a big hill at low speeds (high gravitational potential energy), then race down a slope at break-neck speed (potential transforming into kinetic) until you bottom out and enter a loop (highest kinetic energy, lowest potential energy). At the top of the loop, your speed slows (increasing your potential energy), but then you speed up again and you zoom near the bottom exit of the loop (increasing your kinetic energy), and you're off again!

Here's what you need:

[am4show have='p8;p9;p15;p42;p151;p75;p85;p88;p92;p100;' guest_error='Guest error message' user_error='User error message' ]

  • marbles
  • masking tape
  • 3/4" pipe foam insulation (NOT neoprene and NOT the kind with built-in adhesive tape)

To make the roller coasters, you'll need foam pipe insulation, which is sold by the six-foot increments at the hardware store. You'll be slicing them in half lengthwise, so each piece makes twelve feet of track. It comes in all sizes, so bring your marbles when you select the size. The ¾” size fits most marbles, but if you’re using ball bearings or shooter marbles, try those out at the store. (At the very least you’ll get smiles and interest from the hardware store sales people.) Cut most of the track lengthwise (the hard way) with scissors. You’ll find it is already sliced on one side, so this makes your task easier. Leave a few pieces uncut to become “tunnels” for later roller coasters.

Read for some 'vintage Aurora' video? This is one of the very first videos ever made by Supercharged Science:

Download Student Worksheet & Exercises

Tips & Tricks

Loops Swing the track around in a complete circle and attach the outside of the track to chairs, table legs, and hard floors with tape to secure in place. Loops take a bit of speed to make it through, so have your partner hold it while you test it out before taping. Start with smaller loops and increase in size to match your entrance velocity into the loop. Loops can be used to slow a marble down if speed is a problem.

Camel-Backs Make a hill out of track in an upside-down U-shape. Good for show, especially if you get the hill height just right so the marble comes off the track slightly, then back on without missing a beat.

Whirly-Birds Take a loop and make it horizontal. Great around poles and posts, but just keep the bank angle steep enough and the marble speed fast enough so it doesn’t fly off track.

Corkscrew Start with a basic loop, then spread apart the entrance and exit points. The further apart they get, the more fun it becomes. Corkscrews usually require more speed than loops of the same size.

Jump Track A major show-off feature that requires very rigid entrance and exit points on the track. Use a lot of tape and incline the entrance (end of the track) slightly while declining the exit (beginning of new track piece).

Pretzel The cream of the crop in maneuvers. Make a very loose knot that resembles a pretzel. Bank angles and speed are the most critical, with rigid track positioning a close second. If you’re having trouble, make the pretzel smaller and try again. You can bank the track at any angle because the foam is so soft. Use lots of tape and a firm surface (bookcases, chairs, etc).

Troubleshooting Marbles will fly everywhere, so make sure you have a lot of extras! If your marble is not following your track, look very carefully for the point of departure – where it flies off.

-Does the track change position with the weight of the marble, making it fly off course? Make the track more rigid by taping it to a surface.
-Is the marble jumping over the track wall? Increase your bank angle (the amount of twist the track makes along its length).
-Does your marble just fall out of the loop? Increase your marble speed by starting at a higher position. When all else fails and your marble still won’t stay on the track, make it a tunnel section by taping another piece on top the main track. Spiral-wrap the tape along the length of both pieces to secure them together.

HOT TIPS for ULTRA-COOL PARENTS: This lab is an excellent opportunity for kids to practice their resilience, because we guarantee this experiment will not work the first several times they try it. While you can certainly help the kids out, it’s important that you help them figure it out on their own. You can do this by asking questions instead of rushing in to solve their problems. For instance, when the marble flies off the track, you can step back and say:

“Hmmm… did the marble go to fast or too slow?”

“Where did it fly off?”

“Wow – I’ll bet you didn’t expect that to happen. Now what are you going to try?”

Become their biggest fan by cheering them on, encouraging them to make mistakes, and try something new (even if they aren’t sure if it will work out).

Check out this cool roller coaster from one of our students!

Exercises 

  1. What type of energy does a marble have while flying down the track of a roller coaster?
  2. What type of energy does the marble have when you are holding it at the top of the track?
  3. At the top of a camel back hill, which is higher for the marble, kinetic or potential energy?
  4. At the top of an inverted loop, which energy is higher, kinetic or potential energy?

[/am4show]

Pulse Jet Engine

Friday October 23, 2009

A rocket has a few parts different from an airplane. One of the main differences is the absence of wings. Rockets utilize fins, which help steer the rocket, while airplanes use wings to generate lift. Rocket fins are more like the rudder of an airplane than the wings. A fighter plane is like a cross between a rocket and an airplane, because of the high amount of thrust generated by the engines.

A pulse jet engine is something students make in college engineering courses under the direction of experienced professors. When I was a student, we made a small Pulse Jet Engine out of clear acrylic that burned bright and loud enough to wear eye and hearing protection.

These types of engines are very simple, as they have no moving parts. They've been used on scram jet engines and other types of supersonic craft.  A pulsejet engine works by alternately pushing out a hot breath of air rearward and then breathing in fresh air to replace it.  They can run on gasoline, diesel, or kerosene. 

The video below is for DEMONSTRATION PURPOSES ONLY. Please read text below the video.

Note: Please don't try to make one of these pulse jets! There are videos that will show you how, and not one of them I've found is safe to do without a supervising instructor... in fact, they are highly dangerous because of the types of containers and fuels people have chosen to try. The container must be able to withstand high thermal differentials and pressure changes, and the propellant chosen must not burn too hot or you'll explode the container.

Disappearing Foam Cup

Friday October 23, 2009

This is looks like a chemical reaction but it’s not – it’s really just a physical change. It’s a really neat trick you can do for your friends or in a magic show. Here’s how it works:

[am4show have=’p8;p9;p68;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ]

 

Download Student Worksheet & Exercises

You can use styrofoam beads, packing peanuts, styrofoam packing materials, or even a styrofoam cup and place it in your glass jar containing acetone. Styrofoam is made up of polystyrene foam, which is mostly air (that’s why foam is so lightweight). When you add the foam cup to the acetone, you’re removing the air in the foam which makes it look like you’re dissolving this huge amount of cups (you can go through a whole stack with only a cup of acetone).

Why does this work? You are removing the structure that supports the shape of the foam, and are left with only the foam molecules at the bottom of the container (it will look like a blob). Think about a camping tent: when you take away the poles, what happens to the tent? It loses its support structure and collapses down. The same thing is happening to the foam when you place it in the acetone – you are removing the structure that holds the shape. Acetone is found in most nail polish removers.
[/am4show]

Mousetrap Car

Saturday October 17, 2009
A super-fast, super-cool car that uses the pent-up energy inside a mouse trap spring to propel a homemade car forward. While normally this is reserved for high school physics classes, it really is a fun and inexpensive experiment to do with kids of all ages.

This is a great demonstration of how energy changes form. At first, the energy was  stored in the spring of the mousetrap as elastic potential energy, but after the trap is triggered, the energy is transformed into kinetic energy as rotation of the wheels.

Remember with the First Law of Thermodynamics: energy can’t be created or destroyed, but it CAN change forms. And in this case, it goes from elastic potential energy to kinetic energy.

There’s enough variation in design to really see the difference in the performance of your vehicle. If you change the size of the wheels for example, you’ll really see a difference in how far it travels. If you change the size of the wheel axle, your speed is going to change. If you alter the size of the lever arm, both your speed and distance will change. It's fun to play with the different variables to find the best vehicle you can build with your materials!

Here's what you need to do this project:

[am4show have='p8;p9;p100;' guest_error='Guest error message' user_error='User error message' ]
Materials:

  • Mousetrap (NOT a rat trap)

  • Foam block or piece of cardboard

  • Four old CDs

  • Thin string or fishing line

  • Wood dowel or long, straight piece from a wire coat hanger (use pliers to straighten it)

  • Straw

  • Two wood skewers (that fit inside straw)

  • Hot glue gun

  • Duct tape

  • Scissors

  • Four caps to water bottles

  • Drill

  • Razor with adult help



Since the directions for this project are complex, it’s really best to watch the instructions on the video. Here are the highlights:

1. Tape the dowel to the outside of the wire on the mousetrap car (see image below). When the mousetrap spans closed, the dowel whips through the air along with it in an arc.

2. Attach a length of fishing line to the other end of the dowel. Don’t cut the fishing line yet.

3. Attach one straw near each end of a block of foam using hot glue.

4. Insert a skewer into each straw. Insert a wheel onto each end of the skewer. This is your wheel-axel assembly.

5. The wheels on one side should be close to the straw, the wheels on the other end should have a 1/2” gap.

6. Thread the end of the fishing line around the wheels with the gap as shown in the video.

7. Load the mousetrap car by spinning the back wheels as you set the trap.

8. Trigger the mousetrap with a pen (never use your fingers!). The dowel pulls the fishing line, unrolling it from the axel and spinning the wheels as it opens.

What’s Going On?


Energy has a number of different forms; kinetic, potential, thermal, chemical, electrical, electrochemical, electromagnetic, sound and nuclear. All of which measure the ability of an object or system to do work on another object or system.

In the physics books, energy is the ability to do work. Work is the exertion of force over a distance. A force is a push or a pull.

So, work is when something gets pushed or pulled over a distance against a force. Mathematically:

Work = Force x Distance or W = F d

Let me give you a few examples: If I was to lift an apple up a flight of stairs, I would be doing work. I would be moving the apple against the force of gravity over a distance. However, if I were to push against a wall with all my might, and if the wall never moved, I would be doing no work because the wall never moved. (There was a force, but no distance.)

Another way to look at this, is to say that work is done if energy is changed. By pushing on the non-moving wall, no energy is changed in the wall. If I lift the apple up a flight of stairs however, the apple now has more potential energy then it had when it started. The apple’s energy has changed, so work has been done.

All the different forms of energy can be broken down into two categories: potential and kinetic energy.

My students have nicknamed potential energy the “could” energy. The battery “could” power the flashlight. The light “could” turn on. I “could” make a sound. That ball “could” fall off the wall. That candy bar “could” give me energy.

Potential energy is the energy that something has that can be released. For example, the battery has the potential energy to light the bulb of the flashlight if the flashlight is turned on and the energy is released from the battery. Your legs have the potential energy to make you hop up and down if you want to release that energy (like you do whenever it’s time to do science!). The fuel in a gas tank has the potential energy to make the car move.

[/am4show]

 

Trebuchet

Saturday October 17, 2009

trebuchet23This experiment is for Advanced Students. For ages, people have been hurling rocks, sticks, and other objects through the air. The trebuchet came around during the Middle Ages as a way to break through the massive defenses of castles and cities. It’s basically a gigantic sling that uses a lever arm to quickly speed up the rocks before letting go. A trebuchet is typically more accurate than a catapult, and won’t knock your kid’s teeth out while they try to load it.

Trebuchets are really levers in action. You’ll find a fulcrum carefully positioned so that a small motion near the weight transforms into a huge swinging motion near the sling. Some mis-named trebuchets are really ‘torsion engines’, and you can tell the difference because the torsion engine uses the energy stored in twisted rope or twine (or animal sinew) to launch objects, whereas true trebuchets use heavy counterweights.

[am4show have=’p9;p41;p88;p92;p103;’ guest_error=’Guest error message’ user_error=’User error message’ ]

This is a serious wood-construction project. If you have access to scrap wood and basic tools (and glue!), you have everything you need to build this project. You will need to find heavy objects (like rocks or marbles) for the weights.

We want kids to discover that science isn’t in the special parts that come with a kit, but rather in the imagination and skill of the kid building it. We strive to avoid parts that are specially made just for a kit, molded plastic pieces, etc. and instead use parts that any kid could buy from the store. This means that kids can feel free to change things around, use their own ideas to add improvements and whatever else their imagination can come up with. So on this note, let’s get started.

WARNING: This project requires the use of various hand tools. These tools should only be used with adult supervision, and should not be used by children under 12 years of age.

Tools you’ll need:

  •   Hammer
  •   Electric drill with ¼” bit
  •   Hot glue gun & glue sticks
  •   Measuring tape or ruler
  •   Hand saw & clamp (or miter box)
  •   Scissors
  •   Screwdriver (flathead) or wood chisel

Materials:

  • 7 pieces of ½” x ½” x 24″ pieces of wood stock
  • 2 pieces of ¾” x 24″ wood
  • 1 piece of 3″ x 24″ wood
  • 18″ Wooden dowel
  • Screw eye
  • Nails
  • String
  • Clear tube
  • Rubber mesh

Note: wood pieces may be slightly larger or smaller than specified. Just use your best judgment when sizing.

From ½” x ½” x 24″ pieces of wood stock cut:

  • 3 pieces 5″ long
  • 2 pieces 9″ long
  • 3 pieces 3-1/2″ long
  • 4 pieces 5-1/2″ long

From the dowel cut:

  • 2 pieces 7″ long
  • 1 piece 4″ long

 

From the 3″ x 24″ flat piece of wood cut:

  • 2 pieces 3″ long (one of these has a 1″ square notch in it)
  • 2 pieces 5″ long
  • 1 piece 4-1/2″ long

AND…

  • String should be cut into 2 pieces 14-16″ long
  • The pouch is cut from the rubber mesh and is 5″ x 1-1/2″

Advanced Students: Download your Student Worksheet Lab here!

[/am4show]

TaaDaaaaa!!!

Thursday September 10, 2009

Ever wonder how magicians work their magic? This experiment is worthy of the stage with a little bit of practice on your end.

Here’s how this activity is laid out: First, watch the video below. Next, try it on your own. Make sure to send us your photos of your inventions here!

[am4show have=’p8;p9;p12;p39;p92;p100;’ guest_error=’Guest error message’ user_error=’User error message’ ]
For this incredibly easy, super-amazing experiment, you’ll need to find:

  • a plastic cup
  • hard covered book
  • toilet paper tube
  • a ball that’s a bit smaller then the opening of the cup but larger than the opening of the toilet paper tube (you can also use an egg when you really get good at this trick!)

1. Put the cup on a table.

2. Put the book on top of the cup.

3. This is the tricky part. Put the toilet paper tube upright on the book, exactly over the cup.

4. Now put the ball on top of the toilet paper tube.

5. Check again to make sure the tube and the ball are exactly over the top of the cup.

6. Now, hit the book on the side so that it moves parallel to the table. You want the book to slide quickly between the cup and the tube.

7. If it works right, the book and the tube fly in the direction you hit the book. The ball however falls straight down and into the cup.

8. If it works say TAAA DAAA!

 
Download Student Worksheet & Exercises

This experiment is all about inertia. The force of your hand got the book moving. The friction between the book and the tube (since the tube is light it has little inertia and moves easily) causes the tube to move. The ball, which has a decent amount of weight, and as such a decent amount of inertia, is not effected much by the moving tube. The ball, thanks to gravity, falls straight down and, hopefully, into the cup. Remember the old magician’s trick of pulling the table cloth and leaving everything on the table? Now you know how it’s done. “Abra Inertia”!

So inertia is how hard it is to get an object to change its motion, and Newton’s First Law basically states that things don’t want to change their motion. Get the connection?

Exercises 

  1. What are two different pairs of forces in this experiment?
  2. Explain where Newton’s Three Laws of motion are observed in this experiment.

[/am4show]

Balloon Racers

Thursday September 10, 2009

We’re going to experiment with Newton’s Third law by blowing up balloons and letting them rocket, race, and zoom all over the place. When you first blow up a balloon, you’re pressurizing the inside of the balloon by adding more air (from your lungs) into the balloon. Because the balloon is made of stretchy rubber (like a rubber band), the balloon wants to snap back into the smallest shape possible as soon as it gets the chance (which usually happens when the air escapes through the nozzle area). And you know what happens next – the air inside the balloon flows in one direction while the balloon zips off in the other.

Question: why does the balloon race all over the room? The answer is because of something called ‘thrust vectoring’, which means you can change the course of the balloon by angling the nozzle around. Think of the kick you’d feel if you tried to angle around a fire hose operating at full blast. That kick is what propels balloons and fighter aircraft into their aerobatic tricks.

We’re going to perform several experiments here, each time watching what’s happening so you get the feel for the Third Law. You will need to find:

  • balloons
  • string
  • wood skewer
  • two straws
  • four caps (like the tops of milk jugs, film canisters, or anything else round and plastic about the size of a quarter)
  • wooden clothespin
  • a piece of stiff cardboard (or four popsicle sticks)
  • hot glue gun

First, let’s experiment with the balloon. Here’s what you can do:

[am4show have=’p8;p9;p12;p39;p109;p72;p92;p95;’ guest_error=’Guest error message’ user_error=’User error message’ ]
1. Blow up the balloon (don’t tie it)

2. Let it go.

3. Wheeeee!

4. Tie one end of the string to a chair.

5. Blow up the balloon (don’t tie it).

6. Tape a straw to it so that one end of the straw is at the front of the balloon and the other is at the nozzle of the balloon.

7. Thread the string through the straw and pull the string tight across your room.

8. Let go. With a little bit of work (unless you got it the first time) you should be able to get the balloon to shoot about ten feet along the string.

This is a great demonstration of Newton’s Third Law – the air inside the balloon shoots one direction, and the balloon rockets in the opposite direction. It’s also a good opportunity to bring up some science history. Many folks used to believe that it would be impossible for something to go to the moon because once something got into space there would be no air for the rocket engine to push against and so the rocket could not “push” itself forward.

In other words, those folks would have said that a balloon shoots along the string because the air coming out of the balloon pushes against the air in the room. The balloon gets pushed forward. You now know that that’s silly! What makes the balloon move forward is the mere action of the air moving backward. Every action has an equal and opposite reaction.

Multi-Stage Balloon Rocket

You can create a multi-stage balloon rocket by adding a second balloon to the first just like you see here in the video:

Tie a length of string through the room, having at least twenty feet of clear length.  Thread two straws onto the string before securing the end.  Punch the bottoms out of two foam coffee cups and tape parallel to the threaded straws.

Blow up balloons while they are inside the cups, so they extend out either end.  When blowing up the second balloon, sandwich the untied end of the first inflated balloon between the second inflated balloon surface and inside the cup.  Hold the second balloon’s end with a clothespin and release!

Balloon Racecar

Now let’s use this information to create a balloon-powered racecar. You’ll need the rest of the items outlined above to build your racecar. NOTE: in the video, we’re using the popsicle sticks, but you can easily substitute in a sheet of stiff cardboard for the popsicle sticks. (Either one works great!)

Download Student Worksheet & Exercises

You now have a great grasp of Newton’s three laws and with it you understand a good deal about the way matter moves about on Earth and in space. Take a look around. Everything that moves or is moved follows Newton’s Laws.

In the next unit, we will get into Newton’s Third Law a little deeper when we discuss momentum and conservation of momentum by whacking things together *HARD*. But more on this later…

Exercises

  1. What is Newton’s Third Law of Motion?
  2. Why does the balloon stop along the string?

[/am4show]

[am4show have=’p9;p39;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Advanced students: Download your Balloon Racer Lab here.

[/am4show]

Rocket Ball Launcher

Thursday September 10, 2009

This is a satisfyingly simple activity with surprising results. Take a tennis ball and place it on top of a basketball… then release both at the same time.

Instant ball launcher!

You’ll find the top ball rockets off skyward while the lower ball hit the floor flat (without bouncing much, if at all). Now why is that? It’s easier to explain than you think…

Remember momentum? Momentum can be defined as inertia in motion. Something must be moving to have momentum. Momentum is how hard it is to get something to stop or to change directions. A moving train has a whole lot of momentum. A moving ping pong ball does not. You can easily stop a ping pong ball, even at high speeds. It is difficult, however, to stop a train even at low speeds.

Mathematically, momentum is mass times velocity, or Momentum=mv.

One of the basic laws of the universe is the conservation of momentum.  When objects smack into each other, the momentum that both objects have after the collision, is equal to the amount of momentum the objects had before the crash. Once the two balls hit the ground, all the larger ball’s momentum transferred to the smaller ball (plus the smaller ball had its own momentum, too!) and thus the smaller ball goes zooming to the sky.

Materials:

  • two balls, one significantly larger than the other

[am4show have=’p8;p9;p12;p39;p72;p92;p95;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

Do you see how using a massive object as the lower ball works to your advantage here?  What if you shrink the smaller ball even more, to say bouncy-ball size?  Momentum is mass times by velocity, and since you aren’t going to change the velocity much (unless you try this from the roof, which has its own issues), it’s the mass that you can really play around with to get the biggest change in your results. So for momentum to be conserved, after impact, the top ball had to have a much greater velocity to compensate for the lower ball ‘s velocity going to zero.

You can also try a small bouncy ball (about the size of a quarter) and a larger bouncy ball (tennis-ball size) and rest the small one on top of the large one. Hold upright as high as you can, then release. If the balls stay put (the small one stays on top of the larger) at impact, the energy transfer will create a SUPER high bounce for the small ball. (Note how high the larger ball bounces when dropped.)

What happens if you try THREE?

Read more about impulse here.

Exercises 

  1. What is the mathematical formula for momentum?
  2.  Explain momentum in words.
  3.  What happens to the momentum of the bottom ball in this experiment?

[/am4show]

Aurora’s LEGO Robots

Monday August 17, 2009

Building the perfect robot for the right job.

If you’re new to robotics, LEGO makes it easy to build robots.

Even if you think you’ve outgrown LEGOs, take a second look at the inventions below that I’ve created. Many scientists and engineers got their start building with LEGOs! My kids and I share many LEGO sets together, and my absolute favorite is the 1999 Lego Mindstorms set.

We still use it to build and program robots today! But don’t feel limited to this set, as it’s hard to find nowadays. Use this page as a source of inspiration for your own inventions. Although these are images and not videos, do you think you can still figure out how they move?

Tabletop Cleaner

A combination of the Ultimate Builder’s Set and my own creativeness and a differential light sensor (see below under “sensors”), this little guy can stay on a tabletop with right and left edge detectors, rear edge detector, and avoid obstacles with a left and right bump touch sensors, and can track a beam of light or find a light source using Michael Gasperi’s differential light detector.  Using six sensors mulit-plexed into three available input ports on one RCX, a little creative programming, and three motors (one for the brushes, two for the drive) makes for a cool project!

 

 

 

The Claw IV

One of the first things I’ve built from the Mindstorms box: I added pneumatics and a ball, and suddenly I have a 4-axis grabber arm with a pneumatic claw that picks up balls from one location and deposits them to the target every single time! I must add that if it were strictly open-loop program, it would miss after the second or third try, as it never quite comes back to the same spot. This MEGA CLAW uses four sensors, five motors (three for the three-axis movement, one to operate the pneumatics valve, one as a pump to keep the air tank stocked), one RCX, and one Scout (to handle the extra motor ports).  Sensors detect the mechanical limits of the arm.

I initially wanted to make a 5 or 6-axis arm, but decided to wait until I understood how to get these pieces to fit together more efficiently.

 

Max the Hexapod

I was so intrigued by the idea of a six-legged walker that I went right to the source – Flik by Nick Donaldson and Hexapod by JP Brown and made JP’s posted version of a single RCX Hexapod.  It worked wonderfully!  It took every last LEGO piece I owned to put Max together, as he’s a rather large robot – over 2 feet long, not including the whiskers.

Aft Articulation Point Forward Articulation Point


Killough Platform

This is a Killough drive system from Macs Robotics Page.  This platform can simultaneously rotate while driving forward.  Think of how an office chair’s wheel base rotates around while you push the chair across the
room.

Same assembly three times make up the structure of this amazing robot platform.

 

Synchronous Drive Platform

This is a Synchro motor drive system also inspired by Building Robots with LEGO Mindstorms by Mario Ferrari et al.  The coolness behind this system is the robots ability to turn its wheels in place without
turning the platform – hence this robot does not have a “front”, “rear”, “left”, or “right” – it goes in all directions!

 

Wheel assembly – each wheel is powered and can change orientation.

 

Top view – note that this robot was built upside-down!!

Tricycle Drive

Yet another Building Robots with LEGO Mindstorms inspired design.  I did not have an RCX free when I built this, so I plugged it into the Scout and made both motors go forward.  What was interesting about this was the vehicle initially went straight, then slowed and turned, then reversed direction in the turn, went backward, and began to turn again.  One motor controls the drive, and the other controls the front wheel’s orientation.  So when someone asks, “Can you build a car to go forward and reverse without reversing the motors?” you can say “Yes!”

Twelve-Legged Robot

This robot was inspired by Building Robots with LEGO Mindstorms by Mario Ferrari et al.  The idea is to make a walker platform stable enough to turn tight corners while line-tracking.  The only improvement I would do next time is to couple the motors (independent motors – one per side – in above photo) so it does not have a gradual turn while it walks!

 

MIBO

From Jin Sato’s book, The Master’s Technique, we created MIBO, a LEGO version of SONY’s AIBO – a robotic dog that can sit, shake (sort of), and shuffle along the floor.  He barks (more like a beep, really), and is lots of fun!!!  We’re adding non-LEGO parts, such as a wireless camera and sound sensor for further abilities for MIBO.  (Chasing ball and following a whistle?)  We’re really excited about MIBO and thank Jin Sato for all his hard work!


 

SHRIMP

 

The SHRIMP is a high-mobility wheeled rover designed by the Autonomous Systems Lab in Lausanne, Switzerland.  This innovative rover is capable of climbing over objects 2.5 times its wheel diameter!


 

Whiz

Whiz is a “whiz with sensors!” robot geared for a complex game of RoboTag.  This amazing robot is capable of exploring and reacting to its environment!  Whiz is loaded with a differential light sensor to seek and find
light, a sound sensor to detect and react to sharp sounds, a line-detecting sensor mounted on the front for staying on a tabletop or within a black-outlined rink, and it can avoid obstacles by knowing which bumper – front or back – is triggered.


 

Close-up views of the cool stuff:

Differential Light Sensor

 

Sound Sensor

 

Due to port limitations, I’ve plugged in a relay to switch between the sound and differential light sensor.  The following ports are connected:

Input 1 Touch Sensors (both)
Input 2 LEGO Light Sensor
Input 3 Differential Light Sensor and Sound Sensor
Out A Left Motor
Out B Relay and LEGO Lamps (optional)
Out C Right Motor

 

Front View(Two “eyeballs” are CdS light detectors in the differential light sensor)

Rear View (see the microphone?)

Top View (Blue box on left side is the relay)

Right Profile (Rear -> Front)

Left Profile (Front -> Rear)


Homebrew Sensors & Actuators

These sensors were adapted from Extreme Mindstorms: An Advanced Guide to Lego Mindstorms by Dave Baum, Michael Gasperi, Ralph Hempel and Luis Villa.  Many thanks to all these wonderful inventors for their genius!

This differential light sensor (as described in great detail in Michael Gasperi’s section of the book mentioned above) does a wonderful
job of being a “smart sensor”.  What would normally take 2 of your 3 sensor input ports to tell which way a light source is (to the left or right), this one tells you the difference and takes only 1 input port!  You don’t need the full capacity of the LM324N – if you have a 358 handy, use it.  The larger the CdS photocells, the
better it reacts.  This sensor is excellent for tracking a light source!!  Currently used on Whiz.

A sound sensor initially seemed like a silly idea – especially when Michael Gasperi pointed out that it turned your expensive LEGO robot
into a clapper.  But then, during a game of RoboTag, we realized that it might not be such a bad idea.  It would be handy to have
one robot beep and the other listen and search for it.  It worked pretty well for our application, and allowed us to use multiple robots
to search for different characteristics (light, sound, touch, temperature…).  Currently used on Whiz.

I just had to know what was inside the expensive little light sensor that comes with the RIS.  I was very excited when I found the schematic
online and went to work right away.  I am lucky enough to have a lot of parts on hand, and have noted some standard parts you can use if
you don’t have the oddball ones mentioned in the schematic.  Works great!!  (Not currently used on Whiz)

I figured, if the sensor above can see light, why not add in IR capabilities and find out if it can see the difference between white and
black?  Take out the phototransistor (the transistor in the schematic without a base) and insert an IR detector.  Add in the LED everyone’s
always taking out – but be sure it’s an IR or visible red LED (red LEDs often also emit in the IR range, and you can see if they are on).  If
you wrap the detector in electrical tape to shield it from side-lighting from the LED, it works more accurately.  It has a drop 15-20 (out of
100) between black and white, depending on your lighting conditions. Good enough for line-tracking!  (Not currently used on Whiz)

If you’re short on input ports, and you’ve got two touch sensors to wire to only one port, consider this:  wouldn’t it be nice if the
RCX read one value for one sensor, and a different value for the second sensor?  To make one sensor read differently than another when both
are plugged into the same input, you’ll need to make a special wire for the connection.  Solder in a 22k resistor at the end of one of the
wire leads just before it goes onto the electric plate, and your touch sensor will read about 50, whereas your straight connection (using the
black wires that came with your RIS set for connecting sensors) will read 100.  When you program, pretend it’s a light sensor reading two different values.  Currently used on Whiz.

Buzzing Hornets

Monday July 27, 2009

hornet1Sound is everywhere. It can travel through solids, liquids, and gases, but it does so at different speeds. It can rustle through trees at 770 MPH (miles per hour), echo through the ocean at 3,270 MPH, and resonate through solid rock at 8,600 MPH.

Sound is made by things vibrating back and forth, whether it’s a guitar string, drum head, or clarinet. The back and forth motion of an object (like the drum head) creates a sound wave in the air that looks a lot like a ripple in a pond after you throw a rock in. It radiates outward, vibrating it’s neighboring air molecules until they are moving around, too. This chain reaction keeps happening until it reaches your ears, where your “sound detectors” pick up the vibration and works with your brain to turn it into sound.

You can illustrate this principle using a guitar string – when you pluck the string, your ears pick up a sound. If you have extra rubber bands, wrap them around an open shoebox to make a shoebox guitar. You can also cut a hole in the lid (image left) and use wooden pencils to lift the rubber band off the surface of the shoebox.

[am4show have=’p8;p9;p16;p43;p151;p64;p75;p100;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

  • index card
  • rubber band
  • 3′ string
  • small piece of craft foam sheet OR a second index card
  • hot glue and glue sticks
  • tape

Download Student Worksheet & Exercises

Why is this happening? When you sling the hornet around, wind zips over the rubber band and causes it to vibrate like a guitar string… and the sound is focused (slightly) by the card. The card really helps keep the contraption at the correct angle to the wind so it continues to make the sound.

Troubleshooting: Most kids forget to put on the rubber band, as they get so excited about finishing this project that they grab the string and start slinging it around… and wonder why it’s so silent! Make sure they have a fat enough rubber band (about 3.5” x ¼ “ – or larger) or they won’t get a sound.

Variations include: multiple rubber bands, different sizes of rubber bands, and trying it without the index card attached. The Buzzing Hornet works because air zips past the rubber band, making it vibrate, and the sound gets amplified just a bit by the index card.

Exercises 

  1. What effect does changing the length of the string have on the pitch?
  2. What vibrates in this experiment to create sound?
  3. Why do we use an index card?

[/am4show]

Harmonicas

Monday July 27, 2009

Your voice is a vibration, and you can feel it when you place a hand on your throat when you speak. As long as there are molecules around, sound will be traveling though them by smacking into each other.

That’s why if you put an alarm clock inside a glass jar and remove the air, there’s no sound from the clock. There’s nothing to transfer the vibrational energy to – nothing to smack into to transfer the sound. It’s like trying to grab hold of fog – there’s nothing to hold on to.

[am4show have=’p8;p9;p16;p43;p151;p64;p75;p100;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Here’s what you need:

  • two tongue depressors
  • three rubber bands, one at least 1/4″ wide
  • paper
  • tape

 
Download Student Worksheet & Exercises

What’s going on? The rubber band vibrates as you blow across the rubber band and you get a great sound. You can change the pitch by sliding the cuffs (this does take practice).

Troubleshooting: This project is really a variation on the Buzzing Hornets, but instead of using wind to vibrate the string, you use your breath. The rubber band still vibrates, and you can change the vibration (pitch) by moving the cuffs closer together or further apart. If the cuffs don’t slide easily, just loosen the rubber bands on the ends. You can also make additional harmonicas with different sizes of rubber bands, or even stack three harmonicas on top of each other to get unusual sounds.

If you can’t get a sound, you may have clamped down too hard on the ends. Release some of the pressure by untwisting the rubber bands on the ends and try again. Also – this one doesn’t work well if you spit too much – wet surfaces keep the rubber band from vibrating.

Exercises

  1. What is sound?
  2. What is energy?
  3. What is moving to make sound energy?

[/am4show]

How to Tie Your Shoes

Friday May 29, 2009
You probably already know how to tie your shoes, I know. But what you may not know is how to tie them so they don't become loose easily and are fast to untie... faster than a regular double-knot. Here's how:

[am4show have='p8;p9;p100;' guest_error='Guest error message' user_error='User error message' ]


[/am4show]

Electric Spinning Flyer

Friday May 22, 2009
After you've made the paper flying machines, it's time to step it up and make an electric plane that really flies around in a circle. You can suspend this from a string tied to the ceiling or pop it into the eraser top on a wooden pencil. Either way, it's guaranteed to make you and your cat quite dizzy.

[am4show have='p8;p9;p93;' guest_error='Guest error message' user_error='User error message' ]
Materials:

  • 1 wood pencil with eraser

  • AA battery pack

  • 3VDC motor

  • 5 popsicle sticks

  • 2 alligator clip leads

  • AA batteries for your battery case (Cheap dollar-store “heavy duty” type are perfect. Do NOT use alkaline batteries like Duracell or Energizer!)

  • 1 propeller (rip this off an old toy or hand-held fan or balsa wood airplane)

  • 1 tack


Here's what you do:


This is an excellent demonstration of Newton's Third Law: the propeller generates thrust in one direction, sending the airplane in the other. Since the airplane is attached to the long shaft, it's flight is restricted to a tight circle. It's important to be sure to balance the rod on your fingertip before attaching the tack, or it may not be able to correct this imbalance during flight. Give it a try!

[/am4show]

Ten Static Electricity Experiments to Mystify Your Kids

Saturday March 7, 2009

Plasma ball centerThe smallest thing around is the atom, which has three main parts – the core (nucleus) houses the protons and neutrons, and the electron zips around in a cloud around the nucleus.

The proton has a positive charge, and the electron has a negative charge. In the hydrogen atom, which has one proton and one electron, the charges are balanced. If you steal the electron, you now have an unbalanced, positively charge atom and stuff really starts to happen. The flow of electrons is called electricity. We’re going to move electrons around and have them stick, not flow, so we call this ‘static electricity’.

These next experiments rely heavily on the idea that like charges repel and opposites attract. Your kids need to remember that these activities are all influenced by electrons, which are very small, easy to move around, and are invisible to the eye.
[am4show have=’p8;p9;p20;p47;p76;p97;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Blow up a balloon. If you rub a balloon on your head, the balloon steals the electrons from your head, and now has a negative charge. Your head now has a positive charge because your head was electrically balanced (same number of positive and negative charges) until the balloon stole your negative electrons, leaving you with an unbalanced positive charge.

Let’ play with a more static electricity experiments, including making things move, roll, spin, chime, light up, wiggle and more using  static electricity!

Here’s what you need:

  • 7-9″ balloon (get two in case one pops)
  • a wall
  • wool sweater or scarf
  • sink
  • ping pong ball
  • comb
  • neon bulb
  • tissue paper
  • wire coat hanger
  • tape
  • packing peanuts
  • bubble juice
  • fluorescent bulb (burnt-out bulbs are fine to use)
  • nylon stocking (AKA ‘panty-hose’)
  • plastic grocery bag

Download Student Worksheet & Exercises

Static Electricity Experiments!

Expt. 1: Static Hairdo Charge a balloon by rubbing it on your head for 30 seconds. Pull the balloon up about six inches to check your progress – if the hair isn’t sticking to the balloon, try again on someone with clean, dry hair (without any hair styling goop). When you put the balloon close to your head, notice how your hair reaches out for the balloon. Your hair is positive, the balloon is negative, and you can see how they are attracted to each other!
Your hair stands up when you rub it with a balloon because your head is now positively charged, and all those plus charges don’t like each other (repel). They are trying to get as far away from each other as possible, so they spread far apart. Does the hair continue to stand apart even after you remove the balloon? Does it matter what hair color or texture? (Does the balloon shape matter?)

Bonus Question: How can you get rid of the extra electrons?

Expt. 2: Finding Attraction Rub your head with the balloon and then hold the balloon to a wall. Can you make it stick? How about the ceiling? How many other things does the balloon stick to? (Hint – try a wool sweater.)

Expt. 3 Wiggly Wonder Hold the charged balloon near a stream of water running from a faucet. Can you make the water wiggle without touching it? The charged balloon attracts the stream of water. The water is like a bar magnet in that there are poles on a water molecule: there’s a plus side and a minus side, and the water molecules line up their positive ends toward the balloon when you bring it close.

Expt. 4 Ping Pong Puzzle Rub a comb with a wool sweater, and bring it close to a ping pong ball resting on a flat table. Why do you think the ping pong ball moves? Does it work if you use a charged balloon instead? What if you swap the ping pong ball for a piece of styrofoam?

Expt. 5: Static Neon Store up a good charge of electrons by scuffing along the carpet in socks on a warm, dry day. To make this a much more interesting experiment, hold one end of a neon bulb and watch it light as you touch the other end to a nearby object such as a metal faucet, metal part of a lamp, etc. You can also bring it close to your TV set (the old tube TV kind), both turned on and just turned off, to see if it has any effects on the neon lamp bulb?

Hint: you’ll need to get the neon bulb out of the plastic encasing and hold only one of the wires to make this experiment work – one wire act a as the collector, the other is grounded (via your hand) to the earth. You can also hold onto one lead as you slide down a plastic slide and then touch something grounded (like your mom).

You steal electrons and take on a negative charge when you scuff along the carpet in socks. Remember that just like magnets, ‘like’ charges (negative-to-negative or positive-to-positive) repel, and opposite charges (negative-to-positive) attar, which is why you can make your hair stand up on end by scuffing around a lot. The hairs all become negative, trying to get as far away from each other as they can.

Expt. 6: Electric Tail Feathers Cut a sheet of tissue paper into 12 thin strips, about 1/2″ wide and 8-12″ long. Straighten out a wire coat hanger (snip off the hook part), or find yourself a 10g piece of metal uninsulated wire. Tape the strips to the end of a wire coat hanger (make sure your coat hanger do not have plastic insulation around it – use sandpaper to sand off any clear enamel if you’re not sure). Attach a piece of plastic with tape or clay to the center of the rod, making a V-groove so the handle sits better on the wire. Bring a very charged balloon near the end of the wire – what happens?

Expt. 7: Ghost Words (Although this experiment has also held the name “Ghost Poop”… ) Rub packing peanuts with wool or your hair to build up a strong, quick static charge. Stick the stryfoam to the wall to spell out words. How long do they stay attached to the wall? Does humidity matter? (Try spritzing with a light mist of water).

 

Expt. 8: Static Bubbles Blow a few big, round bubbles (use store-bought bubble solution, or make your own with 12 cups cold water and 1 cup clear Ivory dish soap and a wire coat hanger stretched into a diamond shape). Chase your bubbles with a charged balloon – what happens? Try the comb rubbed with wool – which works better? What other two things can you use to change the path of the soap bubble? (Photo: Tom Noddy, one of the greatest bubble magicians ever – he’s the first one to ever blow a square bubble.)

Expt. 9: Fluorescents Unplugged In a dark room, rub the length of a fluorescent bulb with a piece of plastic wrap (or polyethylene bag or wool sweater) vigorously and then pull your arm away – the bulb should light up momentarily. What other materials cause it to glow?

Expt. 10: Ghost Leg This experiment is absolutely hilarious to watch, but you must be persistent to get it right. On a cold winter day, crank up the heat in your house to warm and dry out the air. You now have the ideal static electricity environment. Take a nylon stocking (just a single knee-length will work, or just use half of a full pair, but roll up the unused half so it’s out of your way) and press the toe part against a nearby wall. Line your other hand with a piece of a clear plastic bag (if the plastic can stretch, it’s the right kind) and rub the nylon stocking vigorously. Now hold the stocking in the air and see if you scrubbed it well enough to charge the stocking with enough static charge so it repels itself and fills out – looking as if there’s a ghost filling out the leg!

Why do these experiments work?

The triboelectric series is a list that ranks different materials according to how they lose or gain electrons. Near the top of the list are materials that take on a positive charge, such as air, human skin, glass, rabbit fur, human hair, wool, silk, and aluminum. Near the bottom of the list are materials that take on a negative charge, such as amber, rubber balloons, copper, brass, gold, cellophane tape, Teflon, and silicone rubber.

When you rub a glass rod with silk, the glass takes on a positive charge and the silk holds the negative charge. When you rub your head with a balloon, the hair takes on a positive charge and the balloon takes on a negative charge.

When you scuff along the carpet, you build up a static charge (of electrons). Your socks insulate you from the ground, and the electrons can’t cross your sock-barrier and zip back into the ground. When you touch someone (or something grounded, like a metal faucet), the electrons jump from you and complete the circuit, sending the electrons from you to them (or it).

The fluorescent bulb lights up when the electrons jump around. The inside of the bulb is coated with phosphor (a white powder) and filled with mercury vapor gas. The phosphor gives off light whenever it gets smacked with UV light. The mercury vapor gives off UV light whenever it gets excited by electricity (movement of electrons). When you rub the outside of the bulb, electrons start to jump around, exciting the gas, which generated UV light, which hits the phosphor and causes it to glow briefly. When the bulb is in balance, it stays dark. If you tip the balance, electrons flow and you get light.

Exercises

  1. Why does the hair stick to the balloon?
  2. How do you get rid of electrons?
  3. Can you see electrons? Why or why not?
  4. Does it matter what kind of hair you rub the balloon on?
  5. How long does the hair continue to stand up after you remove the balloon?
  6. Does it matter what kind of balloon you use?
  7. How fast or slow do you need to rub for the biggest charge on the balloon?
  8. Does hair color matter?
  9. This evening, find an article or story that describes how electricity improves our lives. Bring the article to school. If you bring in an article that no one else brings in, you get extra points.

[/am4show]