# Volume and Pressure Cylinders

1. Feb 28, 2007

### metalmagik

1. The problem statement, all variables and given/known data
Problem comes straight from a 2001 AP Physics B test

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.

Last edited: Feb 28, 2007