Rod OA rotates about O in a horizontal plane. The motion of the 400-g collar B is defined by the relations r = 500 + 300 sin ?t and ? = 2?(t2 ?2t), where r is expressed in millimeters, t in seconds, and ? in radians. Determine the radial and transverse components of the force exerted on the collar when(a) t = 0 ,(b) t = 0.8 s.