A mass less string is wrapped around a uniform disc of mass m and radius `r`. The string passes over a mass less pulley and is tied to a block of mass M at its other end (see figure). The system is released from rest. Assume that the string does not slip with respect to the disc.
(a) Find the acceleration of the block for the case `M = m`
(b) Find `(M)/(m)` for which the block can accelerate upwards.

Answer

(a) `(g)/(2)`
(b) `(M)/(m) lt (1)/(3)`