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: Thermal Physics > Air and Internal Energy

  1. Jun 24, 2005 #1
    This Q has me stumped, I'm still flicking through some web pages and my text book, but been unable to find a useful formula to work it out yet:

  2. jcsd
  3. Jun 24, 2005 #2

    For each molecule, the kinetic energy associated with each degree of freedom is [itex]\frac{1}{2}kT[/itex], so the kinetic energy of each molecule in the O2, N2 mixture is [itex]\frac{5}{2}kT[/itex]. Summing over the entire gas gives the internal energy [itex]U = N\frac{5}{2}kT = nN{_\mathrm{A}} \frac{5}{2}kT = \frac{5}{2}nRT[/itex].

    P.S. Not PHYS1901 by any chance?
  4. Jun 24, 2005 #3
    No. PHYS 1001 actually :eek:
    I just found this forum, looks like a useful resource all round.

    Thanks for clearing that up. My main problem I think is remembering all the letters and where they come from.

    BTW, you have U = N*5/2*k*T = n*N_a*5/2*k*T

    The only thing that changes there is N --> n*N_a

    What is "N" if N=n*N_A

    (Haven't worked out how to use the "Latex" code yet)
  5. Jun 24, 2005 #4
    [itex]k[/itex] is defined as [itex]\frac{R}{N_\mathrm{A}}[/itex], N is the number of gas molecules.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook