[填空题]
A cooling fan is turned off when it is running at 850a d:6aua/np; k0vona 9rev/min It turns 1500 rpy pi t x;1hjp1)uue*6evolutions before it cu p1j6*iu; pt)1hpx yeomes to a stop. (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