[填空题]
(a) What is the angular momentnk3 ;asyg gbr13 1qz/oq m3hv,i45t fovz-at*utr3m v5:ey+d,hva s8w m of a 2.8-kg uniform cylindrical grinding wheel of rad5: r3td wv yas+hv8,meius 18 cm when rotating at 1500 rpm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$