[填空题]
A small 650-gram ball on thdd. w7v /-xghve end of a thin, light rod is rotated in a horizonsg5ask azr: ( ,kw;ra.tal circle of radius 1.2 m. Calcusa sr :.ga(,5wzk;arklate (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. $m \cdot N$