1. The problem statement, all variables and given/known data Problem comes straight from a 2001 AP Physics B test http://img151.imageshack.us/img151/6159/physicscylinderszq4.png [Broken] 2. Relevant equations PV = nRT KE = 3/2KT deltaU = Q+W 3. The attempt at a solution Okay, for the first two (a and b) I arrived at an answer of double the initial pressure of State 1 and half of the initial volume of State 1. This was because after I drew myself a little P vs. V graph, I knew the two States had to be on the same isotherm, so pressure had to increase in order for volume to decrease. Also, I just realized as I write this, if T is constant, in PV = nRT that means nRT is a constant and as P increases, V must decrease. I'm pretty sure that's right, if it's wrong, I would appreciate clarification. For c I got Isobaric, simply because isothermal and adiabatic do not work. For d I got Yes, 4 --> 1 is isobaric simply because I drew a P versus V graph and since it has to go back to the same isotherm State 2 was on, but volume had to decrease, it had to be isobaric. I do not understand e. I'm having a hardtime knowing what the weight does...do you have to use P = F/A? Thanks for any help at all on this, any corrections if im wrong and any elaboration on any topic is greatly appreciated.