Contact forces, coefficient of restitution, and spin rate of golf ball impact

Cochran and Stobbs (1989) gave a very thorough and clear discussion of the impact between a golf ball and a clubhead. They pointed out that some of the initial kinetic energy of the clubhead is lost. They did not provide any explanation of the mechanisms of the energy loss process. For a lofted club face, they showed experimental results that the smoothness of the club face does not affect the ball spin rate. They hypothesized that the friction force which causes the spin is resulted from sliding, and when sliding stops, the “rolling” friction retards the spin.