a horizontal platform in the shape of a circular disk rotates in a horizontal plane about a frictionless vertical axle.the platform has a mass M=100 kg and a radius r=2.0 m.A student whose mass is m=60 kg walks slowly from the rim of the disk towards its center. If the angular speed of the system sis 2.0 rad/s when the student is at the rim, what is the angular speed when he has reached a point r=0.5 m from the center..