Let α denote the angular velocity with which the plane of axes AB rotates about the fixed axis A. Then it is evident that

vB = α·AB,

(5)

and consequently that

α = γ·TB/AB.

(6)

For internal rolling, as in fig. 92, AB is to be treated as negative, which will give a negative value to α, indicating that in this case the rotation of AB round A is contrary to that of the cylinder bbb.

The angular velocity of the rolling cylinder, relatively to the plane of axes AB, is obviously given by the equation—

β = γ − α
whence β = γ · TA/AB

(7)