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Homework Help: Work Done in a polytropic process

  1. Oct 10, 2011 #1
    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. jcsd
  3. Oct 11, 2011 #2


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    Staff: Mentor

    The ln term comes about because the integral of 1/x is ln(x).
    Search wikibooks for polytropic process.
  4. Oct 11, 2011 #3

    Andrew Mason

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    Science Advisor
    Homework Helper

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

  5. Oct 11, 2011 #4
    Thanks a lot, knew it wasn't a hard question was just stuck on the sub part.
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