[填空题]
A cooling fan is turned off when it is running at 850rev/mie oa4 8do4h:oin It turns 1506 m, y3alp.dr daxqwr7ir./mkhjy 4; 90 revolutions before it comes to a st4 ra,yxh ; yr79klwm3pr.6dqij/a d.mop. (a) What was the fan’s angular acceleration, assumed constant? $\frac{rad}{s^2}$ (b) How long did it take the fan to come to a complete stop? s