[填空题]
A small 650-gram ball on the 39tu f ly4c3mt4ok7joend of a thin, light rod is rotated in a haz .(gtm 3dv c/ yj qlvf842.gik+k7toorizontal circle o dct.k8k avo7gz vtmyq3 l2i/fg(j4.+f radius 1.2 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. $m \cdot N$