[填空题]
A small 650-gram ball on the end-f-olil)g:k i of a thizgsb -c*52zm-xzjep0 pm . 7gin, light rod is rotated in a horizontal circle of radius 1.2 m. b-j5mi72xgz zp*sz pgcm0e-. 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. $m \cdot N$