Kinematics of an Ultraelastic Rough Ball

Abstract

A rough ball which conserves kinetic energy exhibits unexpected behavior after a single bounce and bizarre behavior after three bounces against parallel surfaces. The Wham-O Super-Ball® (registered by Wham-O Corporation, 835 E. El Monte St., San Gabriel, Calif.91776), appears to approximate this behavior and provides an inexpensive and readily available model of kinematics quite different from that of a point mass or smooth ball. The analysis is most strikingly illustrated by the fact that the ball returns to the hand after three collisions with the floor, the underside of a table, and the floor. Some questions are raised concerning the dynamics of the collision.