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!

Homework Help: Squeezing a piston and its effect on temperature

  1. Sep 13, 2008 #1
    1. The problem statement, all variables and given/known data
    If a piston is compressed, how is the temperature affected?

    2. Relevant equations
    U=Q + W

    3. The attempt at a solution

    My soln: I thought that U=k.e. = (3/2)nRT=(3/2) pV ?
    Since PV is constant (P1V1=P2V2), shouldnt temperature be constant?

    Answer sheet: My answer sheet says that Q=0 since piston is insulated. and U=W. Since it is compressed, work is done on the gas, increasing its U, which increases T.

    Which answer is correct???
  2. jcsd
  3. Sep 13, 2008 #2


    User Avatar
    Homework Helper

    Hi qazxsw11111,

    (P1V1=P2V2) is not always true; Boyle's law assumes that the temperature and amount of gas is kept constant.

    If the amount of gas is constant, then for an ideal gas you would use:

    \frac{P_1 V_1}{T_1}=\frac{P_2 V_2}{T_2}

    which follows directly from the ideal gas law.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook