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: Thermodynamics: cylindrical figures contains a gas

  1. Jan 11, 2012 #1
    1. The problem statement, all variables and given/known data

    A cylindrical figures contains a gas and we have a piston that is capable of changing the gases volume.
    Initial state: V0=1l P0=10^5p T=300°K

    We pressurize on the piston that has a mass m=300g and a surface S=20cm^2.
    The new temperature T1=540°K

    2. Relevant equations

    Calculate the change in internal energy.

    3. The attempt at a solution

    Well I know that the change in internal energy is: ΔU=W+Q or ΔU=-P1(V1-V0)

    and that p=F/S. but since my teacher didn't explain the lesson well enough I have no clue on how to answer it. Any help would be very well appreciated.
    Last edited by a moderator: Jan 11, 2012
  2. jcsd
  3. Jan 11, 2012 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

  4. Jan 11, 2012 #3
    Re: Thermodynamics

    i believe i would have to use this one right?


    I would get: ΔU=p1(V0-V2)+Q right?
  5. Jan 11, 2012 #4

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    OK, I'll let you off the hook:
    Internal energy for an ideal gas depends only on it's temperature.
    [tex]\Delta U = \frac{3}{2}nR\Delta T[/tex]

    You know the change in temperature - it's given to you.
    You need to find nR.
  6. Jan 11, 2012 #5
    alright i'll give it a try right now.
  7. Jan 11, 2012 #6
    I got n=.0401 by using the equation of ideal gases and i got a change of internal energy as 55J correct?
    Last edited: Jan 11, 2012
  8. Jan 12, 2012 #7
    Is this correct?
  9. Jan 12, 2012 #8

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    I've not done the math so I cannot tell you.
    But it's numbers-in-numbers-out, hard to go wrong.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook