[填空题]
A small 650-gram ball on a m2 wy (q 6rn8thpqysq;-zt2-the7qgw 0ibvy19v;aok+s end of a thin, light rod is rotated in a horizontal circle of radius 1b0yq ;9g+wova1i7v sk .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. $m \cdot N$