1. The problem statement, all variables and given/known data The diagram is attached. The description of the setup is in the second attachment. I do have solutions to the problem, but I don't understand parts of it. Questions: a) What is the initial pressure in the liquid? b) Please show that the magnitude of the tension in the wire is equal to the magnitude of of the spring force on piston B for all positions in process 1-2. c) What is the change in internal energy of the fluid from process 1-2? 2. Relevant equations First law of thermodynamics E2-E1=Q-W The ideal gas law PV=mRT 3. The attempt at a solution a) According to the free-body diagram on the third attachment, (and the fact that in the initial state the spring force Fs is 0) the pressure of the liquid pressure should be equal to PB. However in our solutions, it says initial pressure of the liquid is PA. I'm not sure why this is true. b) When the rope going around the pulley is pushed up on one side because the piston on side A goes up, I don't see how/ why the tension in the spring should change. In our solutions, it says it changes as 2*σ*g*x, where x=upward displacement of piston on side A. c) The pulley does work in pulling the piston in side A up. However in our solutions, is says we can treat the two gases , copper blocks and liquid as a system with no work/ heat exchange with the surroundings. I don't understand why they don't take into account the work by the pulley.