[填空题]
(a) What is the angular momentum of a 2.8-kg uniform cy m)q 4;(c3u nbuq1oettlindrical grinding whee0ls.wp vykon7 .o8t+20zz 7hwn ngx6ol of rn okx0 7op8tzw w+0l7h .sn6zv2n.ogyadius 18 cm when rotating at 1500 rpm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$