[填空题]
A small 650-gram ball on the end of a thoch. /.-wmh brin, light rod is rotated in a hori)u :8)ppig k4l a-qdtnzontal circle of radius ki p)n)aq 8lgp: tu4d-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. $m \cdot N$