[填空题]
An automobile engine slows down from 4500 rpm to 1200 rpm ug26 xj2ul3 *sy) hhhqin 2.5 s/bjiq*l l/ .g- tx/hqs. Calculate (a) its angular acceleration, assumed constant, $rad/s^2$ (b) the total number of revolutions the engine makes in this time. $rev$