[填空题]
A person of mass 75 kg stands at the center of a rotijv3t,wvrco:7a qk3+yer3h m 97juo, ating merry-go-roun;50s2e5hyhmq,nihr b d platform of radius 3.0 m and momh;yhq,05s5n e2rh bi ment 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