# Homework Help: Find the radial acceleration

1. Jul 22, 2013

### student34

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

A wheel with a radius of 0.2 m has a constant angular acceleration of α = 3.00 rad/s^2. Find the radial acceleration.

2. Relevant equations

ω^2 = ωo^2 + 2*α(θ - θo) → ω = √(2*α*θ)

3. The attempt at a solution

ω = √6 rad/s → a rad = 6*0.2 m/s^2 = 1.2 m/s^2

The book has 15.1 m/s^2. Is the book wrong?

2. Jul 22, 2013

### collinsmark

Are you leaving something out of the problem statement?

With a constant angular acceleration, the radial acceleration is not constant. It will change with time.

In your attempted solution, you found the radial acceleration assuming that the wheel starts from rest, and after the wheel rotated an angular distance of 1 rad. Yet none of that was given in the problem statement.

Is something missing?

[Edit: the tangential acceleration will be constant though. But that's not 15.1 m/s2 either.]

Last edited: Jul 22, 2013
3. Jul 22, 2013

### student34

Thank-you so much. I left out a bunch of stuff because I didn't think that it was relevant - lesson learned on tweaking questions too.