[填空题]
(a) What is the angular momentum of a 2.8-kg uniform )ir0cpw zaj,) cylindrical grinding w4g8. ne7zbq7 go)eqcwheel of radius 18 cm when rotating at 1500 rpm?8.4ggzebcewo 7)n qq7 $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$