Homework Help: Double atwood

1. Sep 11, 2012

MeMoses

1. The problem statement, all variables and given/known data

I need to find the equation for the accelerations of the masses on a double atwood apartatus.

2. Relevant equations

F=ma

3. The attempt at a solution
Ok, I made a free body diagram and I think I figure the first part out. The tension on the top rope is twice the lower rope. I get 3 eqations for the forces.
Note: MassA is on the top pull with B and C on the lower
2T - MassA * g = MassA * AccelA
T - MassB * g = MassB * AccelB
T - MassC * g = MassC * AccelC
I also get AccelA = -((AccelB+AccelC)/2) because the average of A and B is simply the opposite of A.
I hope this is all clear and sorry about the formatting. Somehow I'm drawing a blank on solving this system of equations. Im pretty sure I have all that I need but I just can't get it started. Any help is greatly appreciated. Thank you

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