[填空题]
A small 650-gram ball on the end of aa6jpw-n+xf :x y e5aw1 thin, light ro--zde;b2 *bm/rvj a trsxe21zd is rotated in a horizontal circle of radius 1.2 dm bzer v*j2azt/;-res-1 2xb 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. $m \cdot N$
