# Homework Help: Atwood Machine Lab

1. Nov 5, 2008

### BlueMedic

First of all, I'd just like to apologize for me asking for help in my first post. I know that seems kind of lame.

1. The problem statement, all variables and given/known data
The lab involves an Atwood's machine which is basically two masses attached to some kind of pulley system so that if the masses are equal, the system will be in equilibrium. There's a much better explanation on Wikipedia. Our system has two small pulleys at either end.

I'm supposed to come up with the force equations for determining the value of g, but I can't seem to figure out how to factor in friction.

2. Relevant equations

Net Force = ma

3. The attempt at a solution
I drew the free body diagrams for both masses and did all the equations and whatnot to come up with:
$$g=\frac{2d(m_{1}+m_{2})}{t^{2}(m_{2}-m_{1})}$$

Then I realized that I never took friction into account. I was absent for the first day of this lab so I missed most of the data collecting, and all I have written down for friction is that it took .026kg difference in the masses to overcome the frictional force. I'm pretty sure were not supposed to take rotational inertia or something into account since we haven't learned that yet. Any assistance is much appreciated.