[填空题]
A small 650-gram ball on the end of a thin, light rod is rotated ik s/j6i*: na sot4)lbon a hor9z-5h 9wdk2pu 6 kz ,ds;okkqjizontal circle of radidsh-q9dz 5o,pw zk9k jk u26;kus 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. $m \cdot N$
