1. The problem statement, all variables and given/known data: 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. 2. Relevant equations: 2αΔΘ=ωf2-ωi2 3. The attempt at a solution: 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.