# Equation for angular acceleration

1. Nov 13, 2011

### dman_PL

So knowing knowing radius and mass of the object, what is the equation to find angular acceleration?

2. Nov 13, 2011

### sophiecentaur

It's not dependent on either, is it?
Isn't it just dω/dt?

3. Nov 13, 2011

### gordonj005

your question is kind of ambiguous, theres a number of ways to find angular acceleration depending on what you know. for example, if you know its angular speed at one instant, its angular speed at another, and the amount its turned in between then you can solve for the angular acceleration using:

$\alpha$ = (ωf^2 - ωi^2)/2$\theta$

or, instead if you knew the amount of time that elapsed between those velocities:

$\alpha$ = (ωf - ωi)/Δt

theres a bunch of ways you can do it, but just given the mass and radius doesn't tell you very much. the radius helps you find out the angular acceleration and velocity at different points out from your center of mass, or if you have a tangential acceleration and you want to convert to your angular acceleration:

aT = $\alpha$R