Tennis Ball Popper

What you need

  • A tennis ball.
  • A sharp pair of scissors.
  • A smaller bouncy ball or table tennis ball.

What you do

  1. Pierce the tennis ball in the middle with the scissors and cut the tennis ball in half.
  2. Trim the edges of one of the halves so you are left with just slightly less than a hemisphere.
  3. Using your thumbs, push the tennis ball hemisphere inside out.
  4. Once it is inside out, put it on a table yellow fuzzy side up. Put the smaller ball on top, stand back and wait &

What's going on?

The tennis ball is an elastic object. When you play tennis the ball is momentarily squashed when it hits the tennis racket or the ground. A combination of the air inside the tennis ball and the elasticity of the ball itself allows the tennis ball to bounce away from the racket or up from the ground.

In this experiment, turning the tennis ball hemisphere inside out takes work: energy that you are putting in. This energy is stored as potential energy in the inside out tennis ball, until, suddenly, it flips back the correct way and the potential energy is released as kinetic energy, shooting the smaller ball into the air.

Special Safety advice

Don't use a hard ball for the smaller ball as it can be thrown quite far, quite fast. And don't stand directly over it or you might be hit in the face.