[填空题]
An automobile engine slows down frohm0fsv 4,ff(k)0 -dv u ni+matm 4500 rpm to 1200o*jq6qq s7z 4l 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. $rev$