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Relation of pressure with mean-free-path

  1. Jul 20, 2015 #1
    My textbook says "The lower the gas pressure, the higher the mean-free-path".
    But it does not explain why.

    Can someone please explain it briefly? Thank you very much.
  2. jcsd
  3. Jul 20, 2015 #2
    The mean free path is the average length a gas molecule travels before bumping into another gas molecule.

    Other factors being equal, lower pressure means a molecule will travel further before hitting another molecule.
  4. Jul 20, 2015 #3
    But how does it related with the pressure? Why is the mean-free-path high when the pressure is lower? How to explain it in term molecular level?
  5. Jul 20, 2015 #4


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    Better statement: the lower the density, the longer the mean free path.
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