[填空题]
A person of mass 75 kwns*.l kwyf wxd6m 79.g wluu1z7ie 4u4 stands at the center of a rotating merry-go-round platform of radius 3.0 m and uuz47w4uel i1 moment of inertia 920 $kg \cdot m^2$ The platform rotates without friction with angular velocity 2 $rad/s$ The person walks radially to the edge of the platform. (a) Calculate the angular velocity when the person reaches the edge. $rad/s$ (b) Calculate the rotational kinetic energy of the system of platform plus person before and after the person’s walk.$KE_i$ = J $KE_f$ = J