# Homework Help: Work Done in a polytropic process

1. Oct 10, 2011

### juggalomike

1. The problem statement, all variables and given/known data
A gas is trapped in a cylinder-piston arrangement. The initial pressure and volume are 13,789.5 Pa and 0.02832 m^3. Determine the work(kj) assuming that the volume is increased to 0.08496 m^3 in a polytropic process with n=1.

2. Relevant equations
m_1-2=∫PdV from 1 to 2

3. The attempt at a solution

I believe the equation for n=1 i would use is P1*V1*ln(V2/V1), however i have to show how i would get that from the intial integral, and i am completely lost as to how i can get there.

Also if this is not the correct forum for this post i am sorry, please let me know and i will
re-post it in the correct location.

2. Oct 11, 2011

### Staff: Mentor

The ln term comes about because the integral of 1/x is ln(x).
Search wikibooks for polytropic process.

3. Oct 11, 2011

### Andrew Mason

Express P as a function of V and integrate. Since n=1 in $PV^n = K$, this is rather simple.

AM

4. Oct 11, 2011

### juggalomike

Thanks a lot, knew it wasn't a hard question was just stuck on the sub part.