Time for a flywheel to stop, given moment of inertia + a tangential force

[Roomie]

Homework Statement

A flywheel has a moment of inertia of 0.5kgm^2, diameter 0.5m and is rotating at 1000rpm.
A tangential frictional force of 1000N is applied to its rim.
Calculate the time IN MINUTES for the flywheel to stop.

Homework Equations

None given, I assume:

Torque = I*alpha
Angular Velocity = Angular Velocity at t=0 + alpha*t

The Attempt at a Solution

Here is my attempt:
[PLAIN]http://img600.imageshack.us/img600/6962/scan2.png

You can see I get to a final answer, but it doesn't make sense in my opinion since the question asked for it expressed in minutes, why would they do that if it was going to be such a tiny answer?

If someone could check my working and offer any advice it would be much appreciated, thanks!

 

[Dadface]

Hello roomie.I got an answer of pi/30 squared minutes which is what you got.