[填空题]
An automobile engine slows down fromfz4: qegu;lf/hk 9+we 4500 rpm to 1200 rpm in 2.5:pug a xswo: 59s,wu1m s. Calculate (a) its angular acceleration, assumed constant, $rad/s^2$ (b) the total number of revolutions the engine makes in this time. $rev$