Oblique bounce of a double sphere on a horizontal surface

Abstract

The normal coefficient of restitution (COR) for a sphere that bounces obliquely or at right angles on a horizontal surface usually has an approximately constant value between 0 and 1, which are the limits for a completely inelastic or a perfectly elastic collision respectively. Different results are obtained for the bounce of a non-spherical object. Measurements are presented for a double sphere consisting of two golf balls joined together, incident obliquely on a smooth horizontal surface. The COR varied from 0.15 to 1.0 depending on the alignment of the two balls and the incident spin. The results are explained in terms of a simple bounce model where the lower ball slides on the horizontal surface, and in terms of three different values of the COR defined in terms of (a) the bounce height, (b) the vertical speed of the contact point and (c) the ratio of the final to the initial kinetic energy.