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## Homework Statement

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

## Homework 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 :/

## 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?