Once gross slip ceases, the tangential compliance and the inertia of the sphere act very much like a non-linear spring-mass system. Therefore the natural frequency of this system may be expected to depend upon the radius of gyration of the sphere.
This prediction is confirmed by the results presented in Fig. 3. As x is increased (and hence K is reduced), the number of reversals in tangential force during the cycle increases.
The final period of gross slip can be in either direction depending upon the ratio between the period of tangential oscillation and the duration of the impact. This ratio also determines the sign of the angle of reflexion as shown in Fig. 4, where G2 is plotted against x for an angle of incidence of 1.2. However, the range of values of x obtainable with a solid sphere of
varying density is comparatively small.