1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Thermodynamics: Heat and Work in a Cylinder

  1. Sep 7, 2015 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations
    W = ∫pdV
    W = (1/2)*k*(x2212)
    F = p*A
    3. The attempt at a solution
    Assumptions made:
    1. Quasistatic process.
    2. Pressure is constant.

    Force balance on the piston reveals
    -> = <-
    p0*Apiston = patm*Apiston hence p0 = patm = 101 kPa

    From states 1-2 this is a constant pressure process:

    W12 = p0*Apiston*d1 = (101 kPa)(44*10-4 m2)(0.075m) = 33.333 Joules

    From states 2-3 this is both a constant pressure process and a spring compression process (taken separately):

    W23 (const) = p0*Apiston*d2 = (101 kPa)(44*10-4 m2)(0.075m) = 33.333 Joules

    W23 (spring) = (1/2)*k*(x2212) = (1/2)*(9800 N/m)(0.075m)2 = 27.562 Joules

    Total work done from the initial to the final state is equal to the summation of the three works done above:

    Wtotal = W12 + W23(const) + W23 (spring)
    Wtotal = 33.333 + 33.333 + 27.562 = 94.228 Joules of work done.

    Is my approach to this question reasonable? If not what can I do to fix or look up where I've gone wrong?

    As always, every ones help is greatly appreciated.
  2. jcsd
  3. Sep 7, 2015 #2
    Looks good.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted