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Homework Help: Help needed calculating speed distribution

  1. Jan 17, 2012 #1
    1. The problem statement, all variables and given/known data
    I have a sealed container of volume v = x m^3, which holds a sample of y x 10^24 atoms of He gas in equilibrium.
    The distribution of speeds of the atoms is peaking at 110 m s^-1.

    How do I calculate the temperature and pressure of the He gas?
    Which equations would I use to calculate the average kinetic energy of the atoms?

    2. Relevant equations
    I don't know where to start.

    3. The attempt at a solution
    This is what I need help with.
  2. jcsd
  3. Jan 17, 2012 #2
  4. Jan 18, 2012 #3
    Thanks Spinnor,

    I had already accessed these, but I still can't figure it out. I have a whole host of equations (Boltzmann, Boyle, etc...) and I fully understand the concepts involved, but when I wrote "I don't know where to start", I simply meant, I ACTUALLY don't know HOW to start.
    I have the volume of the container (0.10 m^3), the number of helium atoms (3.0 x 10^24) at equilibrium and the peak of the speed distribution of these atoms (1100 m s^-1).

    I have P = N * (m<vx^2. ÷ L^3)
    I know Helium is a monatomic gas and that the mass of one helium atom is 4.0 amu.

    As it is in equilibrium, there are no changes (Δ), so I need to find the value of the temperature FIRST in order to calculate both the pressure, and I need the pressure and the temperature to calculate the KEav of the helium atoms. From this I need to establish the position of the maximum in the energy distribution.

    So everything in this question comes from where to start. Once I get going I have no trouble, because it's only calculations. I therefore need help in "entering" the problem. That's my problem.
    I can't for the life of me and with application find any examples in my own textbooks or other physics books that might give me a template to work from for that "Aaaah!" moment of recognition.

    If you have any ideas to put me on the right path, I'd be grateful.
    Thanks in advance.
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