[填空题]
(a) What is the angular momenf/ gzrz.b38uktum of a 2.8-kg uniform cylindrical grinding whiaz7qj75ckdk* ;lnimzg +7) aeel of radius 18 cm when rotating at 1500 rp7jil )m7q+zg anc;z5*7kiadkm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$