[填空题]
(a) What is the angular momentum 2,cxw542r whj;cf(rwt5 z rtbof a 2.8-kg unif1(t. a6dw lsnsj5xkg1j8tf;korm cylindrical grinding wheel of radius 18 cm fk;t1 .( n 8jgt1sslwxkj6a d5when rotating at 1500 rpm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$