[填空题]
A small 650-gram ball on the end r7 ci:1thozfr *7sb e+of a hh7n/6 qmx6 yu5vp4zz thin, light rod is rotated in a horizontal circle of radius 1.6m6u5v x nhqzzy4hp/ 72 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. $m \cdot N$