[填空题]
An automobile engine slows down fro qv usebd95 f,1c6w29mpgy v2km 4500 rpm to 1200 rpm in 2.5 s. Calculat5ay-x hv2b pevku: :+ie (a) its angular acceleration, assumed constant, $rad/s^2$ (b) the total number of revolutions the engine makes in this time. $rev$