Rotational Motion: Finding Angle of Chalk Line on Rotating Bicycle Wheel

[AJDangles]

Homework Statement

A rotating bicycle wheel has an angular speed of 2.84 rad/s at some instant of time. It is then given an angular acceleration of 1.75 rad/s2. A chalk line drawn on the wheel is horizontal at t = 0. What angle does this line make with its original direction at t = 1.77 s?

Homework Equations

The rotational kinematics equations.

The Attempt at a Solution

Using the equation:

Δθ = ωt + (1/2)(ang. accn)t²

= (2.84)(1.77) + 0.5 (1.75)(1.77)^2
= 7.77rad

I can't get it right. I have a feeling I have to use the angular acceleration to change the angular velocity, but I can't figure out how to do this. It's probably something really silly so if someone could point out what I'm doing wrong it would be much appreciated.

 

[ahsanxr]

Angular acceleration is 1.75, not 1.62

 

[AJDangles]

Angular acceleration is 1.75, not 1.62

Sorry, typo. Fixed now. Answer is still wrong.

 

[AJDangles]

Anybody?

 

[ahsanxr]

Maybe you should subtract 2pi from the answer?