[填空题]
A small 650-gram balln+8vb fr+ gz/vs x7el, on the en,*byoy qi* zyp2ze+j 1d of a thin, light rod is rotated in a horizontal circ, y1bz 2pjz+qy**eoyi le of 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. $m \cdot N$