Work Done in a polytropic process

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Homework Help Overview

The problem involves a gas in a cylinder-piston arrangement undergoing a polytropic process, with given initial pressure and volume values. The task is to determine the work done during the process as the volume changes from an initial to a final state.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the integral for work done in a polytropic process and the specific case when n=1. There is an attempt to derive the work equation from the integral form, with some expressing confusion about the derivation process.

Discussion Status

Some participants have provided guidance on expressing pressure as a function of volume and integrating, while others have referenced external resources for further clarification. The discussion reflects varying levels of understanding and attempts to clarify the mathematical steps involved.

Contextual Notes

There is mention of potential confusion regarding the appropriateness of the forum for the question, indicating a concern about proper placement of the inquiry. The participants are also navigating the specifics of integrating under the conditions of a polytropic process.

juggalomike
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Homework Statement


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.


Homework Equations


m_1-2=∫PdV from 1 to 2


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

Homework Statement


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.


Homework Equations


m_1-2=∫PdV from 1 to 2


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

AM
 
Andrew Mason said:
Express P as a function of V and integrate. Since n=1 in PV^n = K, this is rather simple.

AM

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

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