[填空题]
A person of mass 75 kg stands at the center++ci - saic7 j,fhj+sb of a rotatinic;wat .i w.;8llqh1jg merry-go-round platform of radius 3.0 m and moment of inerlt8.; w jlcah.iqiw 1;tia 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