[填空题]
(a) What is the angular momentum o-8 gq pxczwym()gx4 n21u*sa0cl,m wh f a 2.8-kg uniform cylindrical griqq e1dq 0fg*w-nding wheel of radiqq*q fg-e 1d0wus 18 cm when rotating at 1500 rpm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$