[填空题]
A small 650-gram bal6nh wh:a ik+t:9ygz i+l odu7. 8v;-vwgznvq +prc 8* svrn the end of a thin, light rod is rotated in a horizontal circle of radius wp.scv8q8-guzr rvv + 7* nd;v1.2 m. Calculate (a) the moment of inertia of the ball about the center of the circle, $kg \cdot m^2$ (b) the torque needed to keep the ball rotating at constant angular velocity if air resistance exerts a force of 0.020 N on the ball. Ignore the rod’s moment of inertia and air resistance. $m \cdot N$