Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Numbers if molecules for differnt velocities in gas

  1. Feb 6, 2012 #1

    georg gill

    User Avatar
    Gold Member

    http://bildr.no/view/1099870

    The distribution of velocities of particles in this text is given by f(u) later in the text (the final part) they say that f(u) du gives fraction of gas molecules with speed between u and du+u. I thought that would only give a infinite small number since du is infinite small and not a fraction of the molecules?

    And I also wonder about that in the next sentence they refer to a function that is drawn in figure 5.15 and 5.16. Is this f(u)du? I would have thought it would have to be only f(u) but it does not get through in the text for me which function they mean

    The text is also here in page 162-163 in the link to the whole book:

    http://bildr.no/view/1099870

    (sometimes some pages does not load but if one open it in different readers for the internet one get different pages unavailable each time. But the part of the book with the text that I wonder about is in the link in the beginning anyway)
     
  2. jcsd
  3. Feb 8, 2012 #2

    georg gill

    User Avatar
    Gold Member

    sorry wrong second link dont think it is that important the question is given in the first anyway

    http://books.google.no/books?id=2Ox...Q-oGrDg&ved=0CEQQ6AEwBDgK#v=onepage&q&f=false
     
  4. Feb 8, 2012 #3

    Ygggdrasil

    User Avatar
    Science Advisor

    An infinitely small fraction is still a fraction of the molecules. More importantly, integrating f(u) du from a to b gives you the fraction of molecules with velocities between a and b.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Numbers if molecules for differnt velocities in gas
  1. Be no gas? (Replies: 10)

Loading...