An automobile engine slows down from 3500rpm to 1200rpm in 2.5s. calculate (a) its angular acceleration, assumed constant, and (b) the total number of revolutions the engine makes in this time.

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anonymous · Answer

I already did part a, and got -96.34 rad/s^2. However, I am stuck in the second part. I thought i could use this formula but I keep getting it wrong. $$\theta= \omega _{i}t+ \frac{ 1 }{ 2 } \alpha  t^{2}$$ 

then convert it to revolutions by dividing theta by 2pi.