The radius of gyration of the 14 kg disk about its center of gravity G is k¯ = 400 mm. One end of the spring is attached to the disk at A and the other end is connected to the block B. The disk is in static equilibrium in the position shown when the displacement y(t) = 10 sin 25t mm is imposed on B (t is the time in seconds). Assuming that the disk does not slip on the horizontal surface,

(a) derive the differential equation of motion of the disk in terms of its angular displacement θ; and

(b) determine the amplitude of the steady-state oscillation at point G