[填空题]
An automobile engine slows delabsg9zid;r0 q;eb8gnqr( 5/o i k :7own from 4500 rpmn uo ur-(kf3mb5x :gbe3v:-oq to 1200 rpm in 2.5 s. Calculate (a) its angular acceleration, assumed constant, $rad/s^2$ (b) the total number of revolutions the engine makes in this time. $rev$