Angular Acceleration of Wheels: Solve Homework Problem

[Devin Longo]

Homework Statement

A cyclist starts from rest and pedals so that the wheels make 8.5 revolutions in the first 4.5 s. What is the angular acceleration of the wheels (assumed constant)?

Homework Equations

$$\alpha$$ = $$\Delta$$$$\omega$$/ $$\Delta$$t

The Attempt at a Solution

I converted 8.5 to radians and divided by 4.5. BUT I CANT GET THE RIGHT ANSWER!

 

[rl.bhat]

Use the formula
θ = ωο*t + 1/2*α*t^2 and find α.

 

[Devin Longo]

So, I do that and I get .839. I kept 8.5 as my theta. It still isn't right. What could I be doing wrong?

 

[rl.bhat]

No. The angular displacement θ = 2*π*n, where n is the number of revolutions per second.