# Homework Help: Linear Pressure Voulme?

1. Sep 26, 2009

### He man

1. The problem statement, all variables and given/known data
A Spring loaded piston cylinder device is filled with .5kg of water vapor at 4Mpa, T=400 degrees C. Initally the spring exerts no foce against the piston. The spring constant is .9kN/cm. The piston has a diameter of 20cm. The water now undergoes a process until its voulme is 1/2 the original voulme. find the temperature and specific enthalpy of the water.

3. The attempt at a solution

I have the solution manual with me. But once i peeked at it, i was going about this completely wrong. It says that this is a linear Pressure Volume process so the equation to use is
(P-P1)=c(V-V1).

Where c =42km/A2. where k is the spring constant, m is the mass of water vapor and A is the area.

What exactly are they talking about when they talk about a Linear Pressure Volume Process?
What is the equation (P-P1)=c(V-V1) suppose to represent? What is that constant that they are putting there?