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Star Masses and Radius

  1. Dec 1, 2009 #1
    Sorry noone was answering my question, and I just wanted to get this done:

    1. The problem statement, all variables and given/known data
    ...Hence show that the mass of the star is M = [tex]4\pi[/tex][tex]p_{c}[/tex][tex]\left(R^{3}/3 )[/tex]

    2. Relevant equations
    M(r) = [tex]4 \pi[/tex][tex]p_{c}[/tex][tex]\left(r^{3}/3 - r^{4}/4R)[/tex]
    This is the mass within a radius

    3. The attempt at a solution
    I already found the mass within a radius via intergration (look at relevant equations), and I know that I have to build up an 'infinite' number of radial masses to get the whole mass of the star. But do I use integration on this equation or something else? What do I do?
  2. jcsd
  3. Dec 1, 2009 #2
    Oohh for f_cks sake.... I realised

    Total radius of the star is 'R'. Just substitute that in for [tex]r[/tex] and cancel, since r1 is subjective and doesn't factor for the whole star.

  4. Dec 2, 2009 #3


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    Gold Member

    The total mass of anything is just M=pV where p is the average density and V is the volume. Here V=4/3*pi*R^3. That's that...
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