The width (W) of the transition-bands can be found, similarly, from the geometrical relations between pendulum and disc, as shown in Figs. 5 and 6. In Fig. 5 rod and disc are moving in the same direction, and

w = BB'.

Now

t =w - p ,
r
t =w ,
r'

r'(w-p) = rw,

w (r'-r) = pr',

w =pr'.(4)
r'- r

Fig. 5.