1. The problem statement, all variables and given/known data The double Atwood machine has frictionless, massless pulleys and cords. Determine the acceleration of masses mA,mB,mC, and the tensions in the cords. 2. Relevant equations F=ma 3. The attempt at a solution First I looked down the bottom section. Assuming mB> mA mB*g - FTA = mB*a FTA - mA*g = mA*a I got the following from the equations above, so I think this must be the acceleration for the masses A and B. aA,B = g* (mB - mA)/(mB + mA) Now Assuming mC*g>FTC mC*g - FTC = mC*a This is where I choked. What should be the second equation for this pulley? FTC = 2FTA? If I were to find FTA in terms of mA, mB, and aA,B, would that be enough for aC's equation?