A ring of mass M and radius R lies flat on a horizontal table. A light thread is wound around it and its free end is pulled with a constant velocity `v`.
(a) Two small segment A and B (see fig.) in the ring are rough and have a coefficient of friction `mu` with the table. Rest of the ring is smooth. Find the speed with which the ring moves.
(b) Find the speed of the ring if coefficient of friction is `mu` everywhere, for all points on the ring.
