# Angular acceleration problem

1. Aug 18, 2011

### seboastien

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

angular acceleration of line a= -2w^2 rad/s

what is angular velocity when theta= pi/3?

2. Relevant equations

chain rule

3. The attempt at a solution

w= e^-2theta is my answer, but I know this is wrong

I know that this question is really easy, but I just don't know how to get it

2. Aug 18, 2011

### rock.freak667

Well you should know that α= -2ω2 means that dω/dt = -2ω2

which is an easily solvable DE once you 'separate the variables' i.e. put all the things with ω on one side and t on the other then integrate both sides.

3. Aug 18, 2011

### seboastien

But then I end up with t=1/2w, how do I find the rest of the answer?

4. Aug 18, 2011

### seboastien

5. Aug 18, 2011

### rock.freak667

I now saw that you have ω and θ so forget my above post and replace α with ω*dω/dθ and integrate again. Do not forget the constant of integration which you can find with the conditions they gave you.

6. Aug 18, 2011

### seboastien

Yes, that was my problem all along... I forgot to add the constant!! Thanks.