[填空题]
(a) What is the angular momentum of a 2.8-kg uj + mc4:yxt.61m,ecvvz;n dvqniforbro;1xd:fb*ye1f;flid 6 q cx0) gt6g 2crzo 1m cylindrical grinding wheel of radius 18 cm when rotating at 1500 rxyx r6 l rb2qobf c1zce60;i dfo;1gg:td1*f)pm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$