[填空题]
An automobile engine*kcgitu//g. r n 6l17q.l izgmk3i40dg e 4tja 1lfz9e slows down from 4500 rpm 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. $rev$