Angular Acceleration: Find Magnitude & Direction

[student 1]

Homework Statement

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.

Homework Equations

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

The Attempt at a Solution

 

[G01]

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

Yes that is correct.

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

 

[tiny-tim]

Hi student 1!

(have a pi: π )

A wheel starts from rest and rotates of 2$$\pi$$ radians, sec in 2.00 seconds.
…
B. Find the angle through which the wheel rotates in this time.

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?

 

[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

 

[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.

 

[tiny-tim]

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

θ_f 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?

 

[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?

 

[tiny-tim]

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?

C'mon … commit yourself!

What is a?