# Homework Help: Angular acceration

1. Jul 16, 2008

### student 1

1. The problem statement, all variables and given/known data
A wheel starts from rest and rotates of 2$$\pi$$ radians, sec in 2.00 seconds.
A. find the magnitude and direction of the angular acceleration.
B. Find the angle through which the wheel rotates in this time.

2. Relevant equations
I'm guessing you would use a form of kinematic equation that deals with angular movement instead of linear??

3. The attempt at a solution

2. Jul 16, 2008

### G01

Yes that is correct.

If you have another question, I can't tell you anything else unless you show more work.

3. Jul 16, 2008

### tiny-tim

Hi student 1!

(have a pi: π )
That doesn't make sense …

how can they ask for the angle when they've already told you it's 2π?

(or do you mean 2π radians/sec after 2.00 sec?)

Could you check the question?

4. Jul 16, 2008

### student 1

So, $$\theta$$f=$$\theta$$i+$$\omega$$it+1/2$$\alpha$$t2

With that I know my Initial's are zero because it starts from rest, How do I know my $$\theta$$final

5. Jul 16, 2008

### student 1

I'm sorry this may not help but it moves with a constant angular acceleration to reach an angular speed of 2n radians/ sec in 2.00 seconds.

6. Jul 16, 2008

### tiny-tim

θf is the answer to B.

α is the answer to A.

You have them both in the only one equation.

For two unknowns, you need two equations.

What other equation can you use?

7. Jul 16, 2008

### student 1

Well would you know (a) since it accelerated constantly for 2 seconds to a angular speed of 2n radians/ sec.??? or do you have to have another formula?

8. Jul 16, 2008

### tiny-tim

C'mon … commit yourself!

What is a?