1. The problem statement, all variables and given/known data The double Atwood machine has frictionless, massless pulleys and cords. Determine (a) the acceleration of masses ma, mb, and mc, and (b) the tensions Fta and Ftc in the cords. 2. Relevant equations F=ma 3. The attempt at a solution So I drew free body diagrams for the mass A, mass B, mass C, and the lower hanging pulley. I then computed these equations from F=ma: Fta - ma = maaa Fta - mb = mbab 2Fta = Ftc Ftc - mc = mcac This is all assuming that there is currently no relationship between the accelerations. And this is where I am stuck. I do not know how to represent ac as that of aa and ab. Or maybe that isn't the correct way to solve the system either. The only thing that I assume is that the tensions for ma and mb are the same. Any guidance would be appreciated. Thanks!