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Intro Thermodynamics

  1. Sep 28, 2009 #1
    1. The problem statement, all variables and given/known data

    a) The number of molecules hitting unit area of a surface per second is:
    0.5vnf(v)dvsin(s)cos(s)ds
    Show that the average value of cos(s) for these molecules is 2/3

    b) Using results above, show that for gas obeying Maxwellian distribution, the average energy of all th molecules is (3/2)kT, but the average energy of the molecules which hit the surface is 2kT.

    2. Relevant equations



    3. The attempt at a solution

    For part a, I just integrated sin(s)((cos(s))^2) from 0 to pi. This gives the correct answer, but I'm not sure if its the correct method.

    I know how to find the average energy of all the molecules

    I'm not sure of how to find the average energy of the molecules that hit the surface.
     
  2. jcsd
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