[填空题]
A person of mass 75 kg stands at the center of jlf h7x.hxvs /tiwh x3*,b-)ka rotating merry-go-round pxwzcs.q;iwx w+ cm57.b 8g:m mlatform 8mwwbm. x7gcz c+wsm ;:i qx.5of radius 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