[填空题]
An automobile engine slows down from 4500 rpm to 1200 rpm in1 9rqv:5*z1 5kf zs-cn 5et)vsphedjw 2.5 s. Calcu dtjl.ee2 3:hv7jf p sk;k9ty9late (a) its angular acceleration, assumed constant, $rad/s^2$ (b) the total number of revolutions the engine makes in this time. $rev$