Angular acceleration problem / 99% sure I'm doing right but getting wrong answer

1. Mar 20, 2012

sweetpete28

A toy car is on a circular track of radius r = .274 m. The car starts at initial speed vo = 1.09 m/s, and accelerates at a constant rate to final speed vf = 2.99 m/s while making 0.507 complete revolutions around the track. What is the angular acceleration?

Here is what I did:

distance traveled in radians = (2pi * r)(.507 revolution) = .8728 radians = θ

ω initial = v0 / r = 1.09/.274 = 3.9781 rad/s

ω final = vf / r = 2.99/.274 = 10.9124 rad/s

ωf^2 = ω0^2 + 2αθ

(10.9124)^2 = (3.9781)^2 + 2(.8728)α

α = 59.1 rad/s^2 but this is wrong....What am I doing wrong??? A little frustrated here....any help much appreciated!!!

2. Mar 20, 2012

ehild

You calculated the distance travelled instead of the angle.

ehild