[填空题]
An automobile engine slows down fromw;43vs rl,w0 l+ycjja 4500 rpm to 1200 rpm in 2.4md.(4 sekdpz:w yllp( :a t9azyqi*35 s. Calculate (a) its angular acceleration, assumed constant, $rad/s^2$ (b) the total number of revolutions the engine makes in this time. $rev$