Energy is constantly changing forms and transferring between objects. There are many forms of energy, a few science whizzes may have heard of what is known as the law of conservation of energy: “Energy can neither be created nor destroyed – only converted from one form of energy to another.” Why don’t we explore ‘kinetic’ energy? This is the energy an object has due to its motion. Try seeing for yourself how this works. Use two balls to transfer kinetic energy from a big ball to a smaller one and see what happens!
l A large, heavy ball such as a basketball or soccer ball.
l A smaller, light ball such as a tennis ball or inflatable rubber ball.
- Make sure you’re outside with plenty of room.
2.Carefully put the tennis ball on top of the basketball, holding one hand under the basketball and the other on top of the tennis ball while standing up.
- Let go of both the balls at exactly the same time and observe what happens.
If you dropped the balls at the same time, the tennis ball should bounce off the basketball and fly high into the air. They will hit each other just after hitting the ground. Afterwards, a lot of the kinetic energy in the larger basketball is transferred through to the smaller tennis ball, sending it high into the air.
While you held the balls in the air before dropping them, they had another type of energy called ‘potential energy’. The balls gained this through the effort it took you to lift the balls up, and it is interesting to note what was mentioned earlier, that energy is never lost, only transferred into other kinds of energy.
Balls used in sport generally bounce, whether that is the basketball or the tennis ball used in this experiment. When either of them falls, they initially gain speed – known as kinetic energy. Upon reaching Earth, it collides with our incredibly large planet which is at rest (well sort of but that is another story!).
When the ball slows down it deforms temporarily before bouncing back up as the air in the ball acts like a spring – it compresses and expands again. During the collision, some of the ball’s energy is converted into heat. As a consequence, the ball shoots up with less energy than it had when it reached Earth. Our planet, being so massive, does not move as a result of the collision.
As witnessed due to the experiment, the heavy ball reaches the earth with more energy as kinetic energy is proportional to the mass of the object. However, it may not bounce as high as the smaller ball as, due to its mass, it needs more energy to reach a specific height. Why not try this experiment with different sports balls and see what happens? We know now that when two balls collide, they exchange energy, but how will balls with different masses react with one another?