[填空题]
A person of mass 75 kg stands at the center of a rotating merryrm s1i jkm+h+,t oad66-gopgn,n7,w :pcb-eze p*-round platform of radiz,bp :7n n cpe*w,p-egus 3.0 m and 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