[填空题]
An automobile engine slows down from 4500 f ebm6w lhi0ud62i8n*rpm to 1200jpt r kd9.wk 7vit/kr6q4g0 q( 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. $rev$