at the point of impact of the ball and the plane. This
concept was first introduced by Garwin [2] who used a tangential
coefficient of restitution of one, which is not physically realistic.
Garwin’s model was modified by Cross [3] who employed a
tangential coefficient of restitution a satisfying 0oao1, with the
horizontal velocity of the point of impact of the ball being
reversed and reduced in magnitude by a factor of a in the impact.
Further details of the physics of this model are given in [1],
together with references to other theoretical and experimental
work.