Two identical 4-lb collars, A and B, are attached to a spring of constant 7 lb/ft and can slide on a horizontal rod which is free to rotate about a vertical shaft. Collar B is initially prevented from sliding by a stop as the rod rotates at a constant rate θ0 = 5 rad/s and the spring is in compression with rA = 3 ft and rB = 7.5 ft. After the stop is removed both collars move along the rod. At the instant when the spring is in compression and the total kinetic energy is 100 ft ?? lb, determine

(a) Ar,

(b) Br,

(c) θ

Neglect friction and the mass of the rod.

4lb ... 7 v v 4