(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Horizontal frictionless cylinder piston device- piston is forced againtst a spring which exerts a force directly propotional to the gas volume. Patm (101.13KPa) also acts on the outer face. Considering the gas as a system, calculate the work for the process from an initial state of 200Kpa, 0.1m^3 to a final volume of 0.3m^2. If the spring is taken as a system find the work for the same process.

2. Relevant equations

Work on spring=1/2kx^2

F=PA

W= integral(PdV) (sorry dont know proper equation tools)

PV/T= constant

3. The attempt at a solution

I must be missing something easy, because it doesnt seem like enough info is given.

Anyway

let x=distance the piston moves

V1= Ah = .1

V2=A(h+x)= .3

rearrange gives x=2h

sum of forces=0 at each state (can i do this?)

P1.A= Patm.A+kh

P2.A= Patm.A+k(h+x)

these 2 eqns gives: kx=P2.A-P1.A

use Work on spring:

W= .5*kx*x

W= .5*(P2.A-P1.A)*2h

use Ah=V1

W= P2.V1-P1.V1

this is as far as i have been able to get and i dont even know if im on the right track. It appears i need to calculate final pressure, but i'm unsure how. the answers are given which are 59.74 and -39.48 so have thought about working backwards, but dont know how to go about it

Any help is greatly appreciated

(edited: typos)

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Thermodynamics- work in a cylinder piston device with spring

**Physics Forums | Science Articles, Homework Help, Discussion**