# Rotational Work and a Hamster!

1. Oct 26, 2004

### Hughey85

After getting a drink of water, a hamster jumps onto an exercise wheel for a run. A few seconds later the hamster is running in place with a speed of 0.8 m/s. Find the work done by the hamster to get the exercise wheel moving, assuming it is a hoop of radius 0.10 m and mass 5.9 g.

I'm not sure how to solve this one. I think you use

Work=(torque) x (delta theta)

Torque = rF

but, after that, i'm not sure what theta would be. Am I even using the right set of equations? Thanks for all the help!

2. Oct 27, 2004

### Tide

All you need to do is compare the rotational energy before and after! That will equal the amount of work the hamster did. The rotational energy is half the product the moment of inertia and the square of the angular velocity.

Thanks to ehild for catching my missing 1/2!

Last edited: Oct 27, 2004
3. Oct 27, 2004

### ehild

half of this...

$$E_{rot}=\frac{1}{2}I\omega^2$$

ehild