1. The problem statement, all variables and given/known data String is wrapped around two identical disks of mass m and radius R. One disk is fixed to the ceiling but is free to rotate. The other is free to fall, unwinding the string as it falls. Find the acceleration of the falling disk by finding the lagrangian and lagrange's equation of motion. 2. Relevant equations L = T - V L = ∂L/∂x - d/dt(∂L/∂x-dot) = 0 3. The attempt at a solution my attempt at the solution is in the attachment. I feel uneasy with my choice for the constraint equation. Can anybody take a look and tell me if it looks ok?