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Estimate time scale of expansion of a star

  1. Apr 15, 2016 #1
    1. The problem statement, all variables and given/known data
    A star experiences a sudden increase in pressure to a new value P'. Taking the average density as ρ and the radius R, estimate the time scale of expansion of the star. (Ignore gravity altogether).

    2. Relevant equations
    The only thing I can see in my notes that may (or may not) be related to this is :
    tdynamical ≈ √R3/GM

    3. The attempt at a solution
    I'm not sure how to begin, I thought perhaps I could make an equation of motion for an outer shell and equate this to some kind of pressure but I don't know how/ am quite lost.

    Any help would be much appreciated thanks.
  2. jcsd
  3. Apr 15, 2016 #2


    User Avatar
    2017 Award

    Staff: Mentor

    Did you try dimensional analysis?

    You cannot use G if you should ignore gravity.
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