[填空题]
A small 650-gram ball on the end of a thin, light rod is rotaycd(j 3w,bv ;kt vv92cnmlnei4*1bp) ked in a horizontal circle of radius 1.2 m. Ck2i1 emvbv c* 9lp)nn4alculate (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. $m \cdot N$