[填空题]
(a) What is the angular momentu 0ffu*elu: x(jm of a 2.8-kg unifou gp.lzrz 0hb.d4,gx5rm cylindrical grinding wheel of radius 18 cm when rotating at 150hgxl0z,gb. pd.u 4z5 r0 rpm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$