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!

Average KE of one atom of He

  1. Mar 18, 2009 #1

    jgens

    User Avatar
    Gold Member

    1. The problem statement, all variables and given/known data

    What is the average kinetic energy of an atom of helium gas at a temperature of 20 degrees C?


    2. Relevant equations

    N/A

    3. The attempt at a solution

    Here's my attempt at a solution: Using the equation E = kT/2 for each degree of freedom, I found that KE = 3kT/2 since an atom of He has three degrees of freedom in translational KE. Using this logic I fould that KE = 6.1 x 10^-21 while the correct answer should be 4.0 x 10^-21. Can someone help me understand where my logic/reasoning is incorrect? Thanks.
     
  2. jcsd
  3. Mar 18, 2009 #2

    Delphi51

    User Avatar
    Homework Helper

    Looks okay to me. Someone got the 4.0 answer by just finding kT.
     
  4. Mar 18, 2009 #3

    jgens

    User Avatar
    Gold Member

    That's what I thought my teacher might have done. Thanks!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook