In Section 3 some numerical trajectories of the non-linear mapping are computed and examples given of motions with various numbers of floor to wall bounces. Also illustrated are the parameter spaces of initial conditions required to produce various numbers of bounces off the wall. In Section 4 a scaling invariance is introduced which rewrites the non-linear map of Section 2 in terms of suitable canonical coordinates. This results in a three- dimensional non-linear map, a reduction in dimension by one from the original system.