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Homework Help: Galactic Dynamics questions

  1. Aug 23, 2008 #1
    1. The problem statement, all variables and given/known data
    http://www.mso.anu.edu.au/~kcf/ATA/ATA_assignment.pdf [Broken]
    Question One
    Question 3b
    Question 4b

    2. Relevant equations/Attempt at a solution
    For the first one im not even sure how to approach this, i understand/have poissons equation, general laws of motion and an idea of what relaxation time should be but im not sure how to mathematically define it.

    For 3b i get http://members.iinet.net.au/~housewrk/3rd/3b.jpg [Broken] with L const and im not sure how to go about solving that for the trajectory r(t)

    For 4b I had to hunt around for Jeans' equation (not given in lectures, sort of a read outside the course thing) and using the info in the question used the reduced form of http://members.iinet.net.au/~housewrk/3rd/4b.jpg [Broken] and again not sure how to get a density distribution out of that, as this form seems to treat it on a single particle basis. To be perfectly honest i thought it was a trick question as if theyre massless why should they be influenced by the potential? (we're only considering classical newtonian mechanics in this course, not GR stuff)

    Any help (pointing out my stupid mistakes included, if youre nice) would be greatly appriciated =D

    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Aug 24, 2008 #2
    Nobody? =(
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