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Homework Help: AP Physics Thermodynamics Homework

  1. Sep 24, 2013 #1
    1. The problem statement, all variables and given/known data

    1)The pressure on an ideal gas is cut in half,
    resulting in a decrease in temperature to
    0.604038 of the original value and a change
    in the volume.
    Calculate the ratio of the final volume to
    the original volume of the gas.

    2) Steam moves into the cylinder of a steam
    engine at a constant pressure of 2.6 × 105 Pa.
    The diameter of the piston is 25.6 cm, and the
    piston travels 31.3 cm in one stroke.
    How much work is done during one stroke?
    Answer in units of J

    3)A steam engine has a boiler that operates at
    295◦F , with a temperature of 180◦F.
    Find the maximum efficiency of this engine

    2. Relevant equations
    1) This problem I am not sure

    2)Same thing. I have 40 problems and Im posting the few I dont get. maybe (Qin = Wout + Delta U)

    3. The attempt at a solution
    1) No idea how to attempt.

    2)No idea.

    295F = 146.11 C + 273= 419.11
    180 F = 82.22 C + 273= 355.22

    355.22/419.11 = .84755
    (1 - .84755) = .1524 = 15.24%
  2. jcsd
  3. Sep 25, 2013 #2
    For the first one, since the process is not specified, try using Ideal gas equation.
    For the second, since the process is isobaric use the formula of work done during the process.
    The attempt for the third question is correct.
  4. Sep 25, 2013 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    You should recognize that degrees Rankine is the absolute temperature scale using Fahrenheit degrees:

    deg. R = deg. F + 459.67
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