LAUSR

The impact of a hard ball on a soft surface involves deformation of the surface, with consequent changes in the coefficient of restitution (COR) as the angle of incidence is varied. Experimental results are presented for oblique impacts of a golf ball with grass and carpet surfaces, and the impact of a billiard ball with clay and foam surfaces. It was found that the COR depends on two main factors. One is the usual variation of the COR with impact speed in a direction normal to the surface. The other involves deflection of the ball arising from indentation of the surface. The indentation forms a ramp that acts to project the ball at a steeper angle.