[填空题]
A small 650-gram ball on : gdl9x-huv7db 1bgu9the end of a thin, lighyw+poto4ncs6 a6p z 68t rod is rotated in a horizontal circle of radius 1.2 m. Calculat a6s+t6o8z4 opncpw6ye (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. $m \cdot N$