Remember those colored bouncy balls you played with when you were little? Well have you ever tried to understand the physics behind it? When you drop the ball from your hand, it falls due to gravity. Of course it does, right? Then the ball hits the ground with a certain speed. When the ball is in contact with the ground, its speed is momentarily zero. Well, that’s understandable. Then the ball bounces back up.

Imagine the scenario and think about it.

  1. What is the speed of the ball the moment it changes direction in the air and begins to fall again?
  2. Does it have the same speed that it did when it hit the ground?
  3. If the ball fell and hit the ground a second time would it travel back to the same height that it was thrown from? When would it stop bouncing?

Thinking about energy will help you with the previous questions. What do you know about kinetic and gravitational potential energy? Can you figure out what energy changes the ball goes through while it is bouncing? If you want you can even take a ball and try it yourself. Make a note of the things you observe. When does the ball slow down? When does it speed up?