# Rotational Motion Question

1. Jan 8, 2012

### AJDangles

1. The problem statement, all variables and given/known data
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?

2. Relevant equations

The rotational kinematics equations.

3. 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.

Last edited: Jan 8, 2012
2. Jan 8, 2012

### ahsanxr

Angular acceleration is 1.75, not 1.62

3. Jan 8, 2012

### AJDangles

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

4. Jan 9, 2012

Anybody?

5. Jan 9, 2012

### ahsanxr

Maybe you should subtract 2pi from the answer?

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