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Bouncy balls are a lot of fun to play with. When you drop them, they come right back up. Put a little force into the drop, and they will bounce even higher, sometimes with unpredictable results! Why does this happen? It has to do with the properties of the material it’s made of – rubber.
Rubber is elastic, which means it can stretch and compress, then return to its original shape. If you could see a slow-motion video of a rubber ball hitting the ground, you would see that the force of hitting the ground causes it to flatten a little. Then as the ball returns to its shape, it pushes off the ground and flies back into the air.
How to do the Hot Cold Ball Bounce STEM Challenge
The Challenge: Find out how temperature affects the ability of a rubber ball to bounce.
Materials: Rubber ball, ice, hot pad, hard surface, tape measure
Challenge Criteria: First, measure how high the rubber ball bounces at room temperature. It’s best to test it several times since every bounce will be slightly different. Make sure to simply drop the ball, using no force. Then, cover the ball in a bowl of ice for several minutes to cool it. Test its ability to bounce just like you did when it was at room temperature. Finally, wrap the ball in a warm hot pad for several minutes and repeat the test.
At what temperature did the ball bounce best? How do you think the temperature affected the elastic nature of the material the ball is made of? How do you think this might affect sports played outdoors, like tennis?
Test other types of balls or more extreme temperatures. Note: Have an adult help you find a way to heat the ball safely.