Compact Disc Problem: Average Angular Acceleration

[sukreth]

Homework Statement

The inner and outer radii of a compact disc are 25 mm and 58 mm. As the disc spins inside a CD player, the track is scanned at a constant linear speed of 1.25m/s. The maximum playing time of a CD is 74.0 min. What is the average angular acceleration of a maximum-duration CD during its 74.0-min playing time? Take the direction of rotation of the disc to be positive.

Homework Equations

v=wr
angular acceleration=rw^2

The Attempt at a Solution

I tried to integrate wr somehow, but w is not constant.

 

[G01]

You don't need to integrate.

First of all, \omega, is the angular frequency. Your second formula is wrong. It should read;

a=r\omega^2 where a is the linear acceleration.

Either way, all you should need to solve this is the first formula.

You know that v=1.25m/s.

Can you use this, and your first formula to find the angular acceleration? If so, it should just be an algebra problem to find the average angular acceleration.