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## Homework Statement

:[/B]Your car tire is rotating at 3.5 rev/s when suddenly you press down hard on the accelerator. After traveling 200 m, the tire’s rotation has increased to 6.0 rev/s. What was the tire’s angular acceleration? Give your answer in rad/s2.

## Homework Equations

:[/B]2αΔΘ=ω

_{f}

^{2}-ω

_{i}

^{2}

## The Attempt at a Solution

:[/B]2α(uhh)=(37.7 rad/s)

^{2}-(22.0 rad/s)

^{2}

We have 200m as a distance. With the absence of a tire's diameter, I tried (200 m)/(2πr rads) but again I don't know the radius. The book's solution manual uses ΔΘ=Δx/r and then simply states that the tire's radius is 32cm. I have no idea where this number came from.