Resonance Exerices

Sunday November 29, 2009

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.


Some of these questions you might recognize from the last lesson on potential energy, but we put them here again so you can see how they are inter-related. Have fun!


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Section One:

1. Which of our body parts function as antennae?


2. Why do I call those antennae?


3. Why do we have two ears?


Section Two:

1. Sound travels by waves. Transverse or longitudinal waves?


2. Sound travels faster in air, water, or solids?


3. Why does sound travel faster in that medium?


4. Would sound travel faster on a hot day or a cold day? Why?


5. Which travels faster, light or sound?


6. If you see a firework and hear the sound one second later, how far away is the firework?


7. If you see lightning and hear the lightning 10 Mississippi’s, uh I mean seconds, later, how far is the lightning?


Section Three:

1. If sound is a form of energy, what’s moving?


2. All sound comes from what?


3. What kind of a wave is sound?


4. What does frequency have to do with sound?


5. What does amplitude have to do with sound?


Section Four:

1. What causes sound?


2. What vibrates?


3. What is natural frequency?


4. Why do objects make different noises if they are hit or dropped or plunked?


5. What three things determine something’s natural frequency?


6. What is resonance?


7. If something is vibrating at 30,000 Hz, can we hear it?


8. What happens if energy is continued to be put into something resonating?


Need answers?

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Answers to Resonance Exercises

Sunday November 29, 2009

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Here’s printer-friendly versions of the exercises and answers for you to print out: Simply click here for printable questions and answers.


Answers:
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1. Our antennae are our ears, eyes, and skin.


2. Antennae pick up energy. Our eyes, ears and skin all pick up energy. Our brain then interprets the energy as light, sound or heat. By the way, you may be asking, “What about the nose? Is our nose an antenna”? Not in my opinion. Molecules have to come into the nose and land on smell sensors to register as a smell. Noses detect matter (molecules), not energy.


3. Our two ears, plus our brain allow us to be fairly accurate at knowing where sounds are coming from. The sound will hit one ear before hitting the other and our brain can do the math and figure out which direction.


Section Two:

1. Longitudinal. The waves travel with the medium.


2. Solids


3. The particles are close together. The closer the particles the faster sound travels.


4. A cold day, since the molecules are closer together.


5. Light is much faster.


6. Sound travels 1000 ft/sec, so that firework is 1000 feet away.


7. Take 10 seconds and divide it by 5. So the lightning is 2 miles away.


Section Three:

1. Energy is the ability to move something against a force. In the case of sound, molecules are moving.


2. Vibrations. No vibration, no sound.


3. Longitudinal wave.


4. Frequency determines the pitch of the sound. The higher the frequency, the higher the pitch. The lower the frequency the lower the pitch.


5. The higher the amplitude of the wave, the louder the sound is. Higher amplitude means more energy which means louder sound.


Section Four:

1. Something vibrating causes sound. The sound waves are carried from the vibrating thing to your ears by longitudinal waves.


2. Everything! Couches, clams, mobile homes, they all vibrate.


3. The frequency something tends to vibrate at.


4. They make different noises because they vibrate at their natural frequency. When they are plunked the frequency that they vibrate at causes the sound wave that we hear.


5. Size, weight, and the material of an object determine its natural frequency.


6. Resonance is when something is vibrating at the same natural frequency as something else and causes that something else to vibrate as well.


7. No. Our ears have a natural frequency between 20-20,000 Hz. They will not vibrate at frequencies outside that range so we cannot hear something that vibrates at 30,000 Hz. Our ears can only be resonated by vibrations between 20-20,000 Hz.


8. If something continues to be resonated by something else, the thing that’s being resonated will vibrate more and more. Eventually, unless the energy is stopped or the vibration is slowed, the object being resonated may break. This is how singers can break wine glasses. They can hit a note that resonates the wine glass. As they keep singing, the wine glass vibrates more and more until it shatters!


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