1. The problem statement, all variables and given/known data A pully system with a hanging mass is connected to a winch. The goal is to find acceleration of the mass for a given motor torque. The pully sheaves is considered with no friction, but has a given inertia. I have found the inertia of the winch, but I have trouble calculating the inertia for the wire on the pully. The given information is: n: number of lines in the pully m1: Mass of wire per length dh: difference in height between the lower and upper pully r: radius of the sheaves Is: Inertia of a singel pully wheel 2. Relevant equations How do I calculate the inertia of the wire in the pully system? If I have n lines, I have n+1 number of pully wheels. (As each end of the wire is either connected to the winch or to a fixed point on the ground). Can I just add the constant inertia of each wheel to a total inertia, even if they will move at different speeds (and accelerations)? 3. The attempt at a solution I have solved the problem with the hanging mass related to the motor toque on the winch. I have found the Inertia of the winch drum, which was just cylinder. But the total inertia should be the sum of the inertias of the winch, the wire and the pullys. And I don't know where to start.