[填空题]
(a) What is the angular momentum of a 2.8-kg uniforkc emzivr ;y27lx7uh ,e -5pr,m cylindrical grindin(;pm q0x-zzsj g wheel of radius z;z-xs( 0jqp m18 cm when rotating at 1500 rpm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$