[填空题]
(a) What is the angular momentum of;jyikff k0 n10 a 2.8-kg uniform cylindrical grindia gze9me594xswrea ,1 ng wheel of radius 18 cm sgm z,w4xaar1e95 ee9when rotating at 1500 rpm? $kg \cdot m^2$ (b) How much torque is required to stop it in 6.0 s? $m \cdot N$