[填空题]
A small 650-gram ball on t)tbw,f(b /ydf hanyzkrg x*qxc4fc: /. r. -rw4e end of a thin, light rod is rotated in a horizontal c xr fx ./ *y-cwr4g:raqk4z.cnircle of 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. $m \cdot N$