Torque in circular motion

1. Nov 8, 2009

ryty

1. The problem statement, all variables and given/known data
When play is pressed, a cd accelerates uniformly from rest to 500 rev/min in 3.0 revolutions. If the Cd has a radius of 5.5 cm, and a mass of 20 g, what is the torque?

2. Relevant equations
not sure, this is my problem. i think its torque=angular acceleration*inertia. but i dont know how to turn "500 rpm in 3.0 revolutions" into angular acceleeration

3. The attempt at a solution
nothing, i dont how to make the equations work

2. Nov 8, 2009

flatmaster

You have your analogy from linear kinematics equations to rotational motion equations.

a = delta v / delta t

So the same is true for rotational acceleration, and change in rotational velocity

3. Nov 8, 2009

ryty

but how does torque fit into this equation?

4. Nov 9, 2009

borvis

You can use: $$\omega^{2}=2\alpha s$$ , where $$s=2\pi r * 3$$ (3 times the circumference)

and 500 $$rev/min=4770 rad/sec$$