[填空题]
(a) What is the angular momentum of a 2.84s ;epuw 02vfo-kg uniform cylindrical grinding bck eh8xj:c( pr ta;zk0/5p6bwheel of radius 18 cm p ae5;k80ptbc z:r cxb( j/kh6when rotating at 1500 rpm? $kg \cdot m^2$
(b) How much torque is required to stop it in 6.0 s? $m \cdot N$