Resumen de Energy Losses in a Bouncing Ball
A ball that bounces vertically on a rigid horizontal surface bounces at reduced speed since energy is dissipated during the collision. A simple model of the process shows that elastic energy stored in the ball is dissipated not only when the ball expands but also while it is compressing. Calculations are presented for a “happy” ball and a “sad” ball, based on experimental results.
A common experiment in elementary mechanics is to drop a ball vertically on a horizontal surface to measure the coefficient of restitution (COR).1,2 The coefficient depends on the elastic properties of both the ball and the surface. The essential physics is that the ball and the surface both compress during the bounce, storing elastic energy like a spring, some or most of that energy being recovered when the ball and the surface expand back to their original shape. The impact duration can be estimated from the ball mass and stiffness of the ball and the surface, in the same way that the oscillation frequency of a mass on a spring is calculated. However, the ball bounces after one half period of oscillation since it is not physically attached to the surface like a mass connected to a spring.
