- #1

- 41

- 0

## Homework Statement

The moment of inertia of a fly wheel about it's axis is 20 kg m

^{2}. A constant torque of 40 N m is applied to the initially stationary fly wheel. Find it's rotational KE after 3 seconds assuming there is no friction in the system?

## Homework Equations

KE=[tex]\frac{1}{2}[/tex]I[tex]\omega[/tex]

^{2}

I=mr

^{2}

a=r[tex]\omega[/tex]

^{2}

[tex]\tau[/tex]=Fr , where [tex]\tau[/tex] = torque.

## The Attempt at a Solution

I know I have to work out the angular frequency. Knowing the torque applied to the wheel for a given time I should be able to work out the speed after 3 seconds, but I don't know the radius of the wheel. so I think I need to work out the angular velocity and radius, and then I can work out KE. But I can't see how to do this?

Can anyone give me any advice?