[填空题]
A small 650-gram ball on the end ofhm0 ul/ t y16e37qohs4 4zkkl1exaqwr b+f6:k a thin, light rod is rotatew oro-8zzy 99d tzb:l)d in a horizontal circle o8o-lt d:9 r zyow9)bzzf 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. $m \cdot N$