[填空题]
A small 650-gram ball on the end of a thin,t-ce3e+g bmm. light rod is rotatedmt/ +uydxzz d;y 8gq:7 in a horizontal circle of:zqmg8 zyx+d7/dy ut; 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. $m \cdot N$