[填空题]
(a) What is the angular momentum of a 2.8-kg uniform cylindrical grinding(f 51m 1b*r 2 2hrvbnotuu7pmy whl.nmoduxgm 2)pwe:( mx6*qk+vqn0h6 eel oq:.gmdmwp (meo q *v)+0 xnx2un6h 6lkf radius 18 cm when rotating at 1500 rpm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$