[填空题]
(a) What is the angular momentum of a 2.8-k( xy n2xyp8 vixar93d7g uniform cylindrica;fncuwgc-, qu .j /2b.pu+saal grinding wheel of ra+nqgus,;ucpu.ja f-2.ca/ wb dius 18 cm when rotating at 1500 rpm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$