[填空题]
(a) What is the angular momeng6;.e r,+qvg1+no vazalo2m g tum o 8suel 8n+f7uif a 2.8-kg uniform cylindrical grinding wheel of rals +u7n 8uei8fdius 18 cm when rotating at 1500 rpm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$