[填空题]
A small 650-gram balvd )vdapd2o)7npqq 7 5* vz6bp3u jy)xui+: )xwmdy2a l on the end of a thin, light rod is rotated in a horizontal circle of radius 1.2 m )xywb 2)+6:xzmypd vu3*a uij. 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. $m \cdot N$