[填空题]
A small 650-gram ball on thot)gbj7fu2 n/e end of -)+at onr nv+cy;0csy a thin, light rod is rotated in a horizontal circle of +cv-n ayt)y sc;r0+noradius 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. $m \cdot N$