How do you make a ping-pong ball bounce even higher?

Ping-pong balls are made to bounce well, but with a simple cup of water, we reach new heights!

What do you need?

• 1 ping-pong ball

• 1 cup

• water

Do this experiment outside or in a place that is allowed to get wet.

Getting to work!

Step 1: Drop a ping-pong ball on the floor. See how high it bounces.

Step 2: Fill a cup with several centimetres of water. Half-filled is plenty.

Step 3: Make a twisting motion with the cup. Make a small whirlpool like this.

Step 4: Carefully drop the ping-pong ball into the cup of water. Thanks to the vortex, the ball stays nicely in the middle of the water.

Step 5: Next, drop the cup of water, with the ping-pong ball inside, straight down. What do you think will happen? Try it out.

What's happening?

The cup of water remains standing, but the ping-pong ball bounces from the cup. It flies very high.

Why though?

When you hold the ping-pong ball in your hand, it gets energy: 'gravitational energy'. When you then drop the ball, that gravitational energy is converted into motion. Or rather 'kinetic energy'.

When the ball collides with the ground, it also bounces back up thanks to that energy. Furthermore, when colliding, part of the energy is converted into sound or heat. As a result, the ball does not bounce as high as from where you dropped it.

You see: energy doesn't just disappear. It can, however, be passed on or converted into another form of energy. We call this the law of conservation of energy.

In this case, you drop the ping-pong ball at the same time as a cup of water. Then not only the ping-pong ball, but also the cup of water has a lot of energy. When the cup of water hits the ground, the water cannot rise back up. The ping-pong ball is in the way. So the water transfers its energy to the ping pong ball. As a result, it suddenly has much more energy to bounce upwards. And we see that: the ping-pong ball flies much higher!

Where else do you encounter that?

In billiards, you are always passing on energy. First from your cue to the white ball. Which in turn passes on its energy to the next ball it bumps into. Again, some energy is converted into sound and heat. As a result, the balls eventually stop.