A man of mass m1 stands on the edge of a horizontal uniform disc of mass m2 and radius R which is capable of rotating freely about a stationary vertical axis passing through its centre. At a certain moment the man starts moving along the edge of the disc; he shifts over an angle φ` relative to the disc and then stops. In the process of motion the velocity of the man varies with time as v`(t). Assuming the dimensions of the man to be negligible, find:
(a) The angle through which the disc had turned by the moment the man stopped;
(b) The force moment (relative to the rotation axis) with which the man acted on the disc in the process of motion.