This lesson may give you a sinking sensation but don’t worry about it. It’s only because we’re talking about gravity. You can’t go anywhere without gravity. Even though we deal with gravity on a constant basis, there are several misconceptions about it. Let’s get to an experiment right away and I’ll show you what I mean.
If I drop a ping pong ball and a golf ball from the same height, which one hits the ground first? How about a bowling ball and a marble?
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I tested this with a golf ball and ping pong ball with a 240fps slomo camera and we dropped the balls from 2 stories (25ft) and the golf ball hit the ground about 0.15 seconds faster
Our crew loves your program. Science is their favorite subject now. They use science jargon all the time too. Instead of, “Pass me the sucky thingy” they say, the eye dropper” and they name the parts of a microscope, osmosis….goodness the list goes on and on. In addition Aurora has such a happy, calm teaching style that she helps me, too. She is an excellent reminder to have fun with learning and relax, make a mistake and try again.
Thanks so much for all you do! Congrats on Cathy Duffy putting you all on her “best” list! She is tough to please and you all passed with flying colors.
Kimberly
Not quite. The atmosphere is what slows things down if they are a different size/shape. For example, if you take two pieces of paper and crumple one into a tight ball… they both weight the same, right? What happens when you drop both from the same height at exactly the same time?
Now try dropping a golf ball and a ping pong ball. These both are about the same size and shape, only the golf ball is heavier. What happens when you drop both from the same height at exactly the same time?
If you repeat this experiment on a moon or planet without an atmosphere, like the moon, in both cases, the objects would hit the ground at the same time. That’s what the hammer and feather experiment were showing. Gravity pulls on all objects equally, it just gets more complicated when an atmosphere (a “sea of air”) is also involved because it affects how things fall as well.
So if you drop 2 things on earth & in space they are going to hit at the same time ( the 2 things ) no matter if you are on the earth or on the moon?
Thanks
It does seem odd, doesn’t it? It’s SHAPE, not density that matters with things falling. A golf ball and a ping pong ball are the same size and shape, and they hit the ground at the same time. But they are different weights (the golf ball is more dense it has more mass for its size). It’s because we live in an ocean of air called an atmosphere, and those air molecules need to be pushed out of the way to make way for the object falling through it. That’s why shape matters, not weight.
I just don’t understand why different things fall at the same time if they are heavier. And why in forever falling the pennies hit the ground at the same time.
You need to be logged in for them to appear… double check that? The exercise questions are at the very bottom right above the comment section. The PDF download is under the first video. If the link doesn’t work, try a different browser – like IE or Safari.
Hi, the link to the student exercises is not there, I did find the link in the comments, just an fyi to your tech person.
Make sure you’re logged in first. What web browser are you using, and it is up to date? What happens if you try a different computer?
i am trying to view the weithy issue vidio but it won’t work
Are you referring to the worksheets/exercises download? You’ll need Adobe Acrobat Reader in order to view the file. Click here for the direct link to the PDF.
I am unable to view the student documents for the pingpong and golf ball. Can you email them to me?
The video should be working now!
The video of the astronauts performing the experiment does not work. We were really looking forward to watching it. Will you be able to fix it?
That’s Tycho Brahe… he’s got quite a reputation, as you’ll find out!
How do you spell the name of the guy who first came up with research and testing rather than just arguing about stuff? You mention him in the first video on the gravity experiments page. Would be great to put him on our history timeline.
Thanks.
Hmmm… well, that would be a little tougher to do than you think. Since the 777 is made from steel and aluminum (among other things), you’d have to figure out how close the magnet was to the plane, which is going to change based on where you stick your magnet. The magnet will cause an electric field to flow in the parts of the plane that are metal, which in turn will set up another magnetic field, so you’ve actually changed part of the problem already. And since the airplane is long, the magnetic force the nose experiences is different than the tail feels… confusing, isn’t it? Learn more about magnetism equations here (bottom of the page): http://en.wikipedia.org/wiki/Magnetic_field
Your best bet is to just “try it”… so try this – the floating magnets experiment: hot glue a magnet to a small block of foam. Make a couple of these and take a bath with your new toys. (This experiment is outlined in detail in Unit 11.) You’ll be surprised how the form perfect geometric vertices depending on how many you float in the tub.)
Hi Aurora
We’ve just watched your forces videos and done some experiments – we really enjoyed them and I really like playing with magnets! I have a question for you, how could you work out how many magnets would pull a Boeing 777?
Thank you
James (aged 8 ) Berkshire, England
Yes, the shape is all spread out, like a sheet of paper versus a wadded up ball of paper. The air has to go all the way around the paper to get past it.
Hi Aurora!
I’m wondering how does the air resistance work on a feather? Is it because of the shape of the feather?
-Dayini (12) 🙂
If you have a heavier and lighter object that are stuck together (as with your stuffed animal with the weighted bottom), the heavier end has more mass per surface area than the lighter end. The resistance from the air slows the fall of the lighter end and so the heaver end will fall first. (If both ends had the same mass-to-surface-area ratio (like a golf ball and a ping pong ball stuck together), then they fall at the same rate. The only thing that makes a lighter object fall more slowly than the heavier is the resistance from the air. Does that help?
Hi Aurora!
We have a question about gravity. We have a stuffed animal that is heavy on the bottom but light on top. When we drop it (and If weight doesn’t matter) why does the heavy side always flip around and hit the ground first? Thank you so much for all the fun we’re having:)
Naomi (10), Lauren (10), and Ella (7)
Bouncing and jumping are not quite the same thing.
A ball will bounce because it has a high ‘elasticity’. If you squeeze the ball, you can feel the ball pushing back on your hand, the same way as it pushing on the floor when it hits. This is what makes the ball bounce. When you squished it, it wanted to be round again. How elastic is a hammer? Not very much, is it? That’s why a ball bounces but not a hammer.
How is a bounce different from a jump? When you jump, you push off from the ground. A hammer can’t do that.. and as it turns out, it doesn’t bounce, either (at least, not very much). Does that help?
Why if you jump on the moon do you bounce back up but the hammer and feather did not bounce on the moon in the video?
Son – age 10
Here’s a great and easy way to do this experiment.
Take two identical water bottles.
Empty one of the water bottles and put the cap back on.
Now you have to identically sized objects with very different weights to experiment with.
Drop them from 5 to 6 feet high and have your partner put his head on the floor to watch which one hits first!
NO!!!!! This is one of the BIGGEST MISTAKES that is still in textbooks! AARRGG!!! (Sorry – I am trying hard not to bang my head on the table too hard…)
Okay, so here’s a question for you (and this is the very same question I asked my own 4th grade teacher, whose response was a blank stare):
If there’s no gravity in space, what keeps the planets orbiting the sun? Why don’t they go flying off in a straight line? Like when you swing a bucket around in a circle and then let go… it goes flying off in a straight line, right? What’s keeping the planets in a circle around the sun?
You’ll often see a picture of an astronaut “floating” right next to the words: “Why does this astronaut float in space? Because there’s no gravity in space.”
That’s ridiculous! If there was no gravity in space, wouldn’t the moon go veering off in a straight line? Wouldn’t the planets stop orbiting the sun?
Sometimes you’ll also see words to the effect of: “You need to be free of the Earth’s gravitational pull to experience weightlessness.”
Another ridiculous statement. You can experience freefall right here on Earth. Just go into an elevator to the top floor and cut the cord. You’ll be in freefall in a very short amount of time.
If while in this freefalling elevator you took a ball out of your pocket and let it go, you’d see that it falls with the same acceleration that you do and will appear ‘weightless’.
So yes, there is gravity in space (especially at the distances you were talking about). If you go into deep space really far away from ANY other object, then yes, you would no experience a pull in any particular direction due to mass, because there’s no mass out there.
Are you wondering if there’s gravity in space why the astronauts float? It’s because he’s in freefall. I wrote a small section about this in Unit 7 already. I am actually going to do a whole segment on this topic and finish it with talking about black holes because there’s so much wrong information out there about this. Look for it soon!
My science textbook I have here says that astronauts float around the space station because there is no gravity in space. Is that right?
This is coooool!
Hi Allison,
It sounds like you have it. Here’s the highlights to remember:
All bodies (objects) have a gravitational field.
The larger a body is, the greater the strength of the gravitational field.
Gravity accelerates all things equally. Which means all things speed up the same amount as they fall.
Gravity does not care what size things are or whether things are moving. All things are accelerated towards the Earth at the same rate of speed.
Gravity does pull on things differently. Gravity is pulling greater on objects that weigh more.
Weight is a measure of how much gravity is pulling on an object.
Mass is a measure of how much matter (how many atoms) make up an object.
My kid is putting together a power point presentation (and giving credit to SUPERCHARGEDSCIENCE.COM!!) Is it correct to say:
Gravity does pull on things differently which is why some things weigh more than others. An elephant weighs more (has more mass) than a feather.
Gravity is pulling greater on objects that have greater mass.
Wow… neat idea!
My child dropped 3 feathers and a flower petal. One of the feathers was from a baby bird and the other two were from a adult bird. It was interesting to note that the 2 adult feathers hit the floor at the same time. He then dropped the adult feather and the flower petal. Both hit the ground at the same time as well. He then thought the baby feather and the adult feather would both fall at the same speed. Both of the feathers seem to be the same size and shape. He knew it was a baby feather because it felt softer then the other feather. They seem to be the same weight but obviously not because the adult feather hit the floor first. Conclusion from child: maybe baby birds have wings that are different from adult feathers so when the baby takes it’s first flight and falls– it won’t fall as fast and get as hurt as it would when it’s an adult.
I wanted to share this with you. This program is really making him think. Thank you!!!!
Thanks for making this so easy to understand-my kids just love it! The video is really interesting, too.
Thank you!
I like this expirement a lot because you can drop so many things together!
seva cable, 9 yrs. old.