[填空题]
(a) What is the angular momentum o0r0y5gnq atd3 f a 2.8-7kkg(qxv pe(w /qoj33m:ljh//n je 9mkg uniform cylindrical grinding wheel of ra xl em(mk3k/evph: jw/j7 j3q( o9/ngqdius 18 cm when rotating at 1500 rpm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$