1. The problem statement, all variables and given/known data If a bike wheel rotates 9.4 times while slowing down to a stop from an initial angular velocity of 8.1 rad/s, what is the magnitude of the angular acceleration in rad/s/s 2. Relevant equations α = at / r α = ω / t α = Θ / t^2 ω = Θ / t ω = v / r Θ = ω t + 0.5 α t^2 v final = v initial + at → ω final = ω initial + αt some of these formulas may be useless, and there possibly are some others not mentioned that i do not know :/ 3. The attempt at a solution Knowing the initial angular velocity is 8.1 and the final is 0 since the wheel stops, i used ω final = ω initial + αt 0 = 8.1 + αt it spins 9.4 times in the time frame during which it slows down, but the radius of the wheel is not given. And i do not know which ω to use in the equation ω = Θ / t in order to find time. If i could get time, then i could use the equation α = ω / t or α = Θ / t^2. Am i even approaching this correctly? if not can somebody point me in the right direction?