Bouncy Ball

At the robotics sleepover last weekend, we started playing with a super bouncy ball. Apparently you can throw it around 25 feet or more up if you throw it at the ground really hard. Since I was weak, I could could only get it 15 feet or so, but the first thing that this made me think of was conservation of energy. (Yes, I know, physics geek. :P)

Since the ball bounces really high, most of the energy of me throwing the ball downwards must go back into the ball as it bounces back up. For most balls, the kinetic energy of throwing the ball goes into sound or other forms of energy when it hits the ground, but for this ball most of the energy must go into potential energy and then kinetic energy. If you calculate that the ball goes 25 feet up, since the acceleration of gravity is -9.8 m/s^2, the velocity of the ball at the bottom was 22.1 m/s. This means that it's initial KE was 1/2mv^2, so if you pretend that the ball was 0.2 kg, then the KE is equal to 98 J. At it's highest point, the PE must be near 98 J, and most of it must not be lost if it goes so high on the next bounce.