Angular Accerlation Homework: Avg. Angular Acc in Rad/s2

[cstout]

Homework Statement

During normal operation, a computer's hard disk spins at 7200 rpm. If it takes the hard disk 3.7 s to reach this angular velocity starting from rest, what is the average angular acceleration of the hard disk in rad/s2?

Homework Equations

Change in Angular Accerlation/ Change in time

The Attempt at a Solution

I tried the above equation but the online homework says the answer is wrong. I'm not sure of what else to do.

 

[G01]

If you don't show your work, how can we know where you went wrong?

Also, your equation given is not an equation (there is no equal sign), but either way, change in acceleration/change in time is a rate of change of acceleration, which would not help you here. Did you mean this?

$$\alpha=\frac{\Delta \omega}{\Delta t}$$