Kid Question: Why do balls bounce?

by Deb on September 12, 2011

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I suspect big girl was actually asking this to delay being kicked outside, because bouncing the little rubber ball down the hall was not going down well. But it’s a good question anyway, and like all good distractions it led to lots of other things to do.

Bouncing balls is a fun one because kids can actually feel the answer for themselves.

  • Get a ball, or better yet several different balls and try to squash them between your fingers.
  • Make a note of which ones squash the easiest.
  • Now bounce them and see which ones bounce the best.

When you bounce a ball it is being squashed against the ground. It has lots of energy from speeding down, when it hits the ground some of that energy goes into squashing it. Then it springs back into shape, and the ball pushing back out also pushes it up into the air again.

Have a look at this video to see it happening in ultra-slow motion.

There are lots of fun ways to play with bouncing:

  • Compare different balls to see which bounces the best. Some of the things that make a difference are what the outside is made of and what is inside – is it hollow or solid?
  • Compare bouncing with using a racquet or kicking against a wall.
  • Hold two balls together with one on top of the other and drop them. The bottom one will stay fairly still and the top one will shoot off quickly. What is happening is that they both deform, but rather than the bottom one’s energy going into bouncing it, when it pushes back to round it pushes the top one, so it gets double the energy.

Now find all your balls and have fun playing!

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{ 1 comment… read it below or add one }

Mrs Green @ littlegreenblog.com September 12, 2011 at 7:31 pm

What a fun post! (I too send my DD outside when she’s trying to bounce balls inside LOL!)

Today, she asked me (as she was lying on her surf board in the bath LOL!) why the surf board sank in the bath but floated on the sea… I’d love you to share your wisdom on that one if you could – I figured it was to do with displacement and that there was a lot more water in the sea; but I wasn’t really sure …
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