Bouncing with energy
Stand clear! How far will the basketball go?
What you need
- basketball
- small inflated rubber ball (lighter than the basketball)
What to do
- Go to an open space outside.
- Hold the basketball in one hand and use your other hand to carefully balance the small ball on top of the basketball.
- Gently hold the small ball in place and drop the two balls at exactly the same time. When the balls hit the ground, the small ball will bounce high into the air.
- Repeat the activity with the balls reversed so the basketball falls on top of the small ball.
What's happening?
This activity demonstrates how energy can be transferred from one object to another. When the two balls are held above the ground they have potential energy and when they are dropped they gain kinetic energy as they fall to the ground. After colliding with the ground, the basketball bounces up and hits the small ball. A lot of the basketball’s energy is transferred to the small ball, giving the small ball enough kinetic energy to fly high into the air.
This dramatic effect results from the difference between the masses of the two balls. The kinetic energy of an object is proportional to its mass so if the basketball is a lot heavier than the small ball, it will have a lot more kinetic energy when the two balls hit the ground, assuming the balls are travelling at the same speed. Most of the basketball’s energy can be transferred to the small ball, causing the small ball to move quickly and fly a long distance while the basketball bounces to a much lower height.
Swapping the positions of the balls in Step 4 demonstrates the fact that the small ball doesn’t have enough energy to transfer to the basketball and the small ball is squashed under the weight of the heavy basketball.
