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Homework Help: Rearranging an equation for pressure

  1. Sep 15, 2004 #1

    I'm having big problems rearranging the following equation which calculates the pressure at the centre of Earth, to find R:

    P = 2(pi*G/3)*ρ2 R2

    Logically to me it would be:

    R = 2(pi*G/3P)*ρ2 square rooted (but i'm pretty certain this isn't right!)

    I've spent ages trying to sort it out and have resorted to randomly placing the figures in an attempt to find R (radius of the earth which is known already)!!

    If anyone could help me sort it out in my head so that I can then rearrange the equation it would be much appreciated!!
  2. jcsd
  3. Sep 15, 2004 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Starting with:
    P = 2(pi*G/3)*ρ2 R2
    Isolate R2:
    R2 = 3P/(2 pi G ρ2)
    Now take the square root:
    R = 1/ρ sqrt(3P/(2 pi G))
    Last edited: Sep 15, 2004
  4. Sep 15, 2004 #3
    We need batter graphics. I'm having a hard time reading equations while trying to decipher the notations.
  5. Sep 15, 2004 #4
    What you did was on the left you should have gotten (1/R) not R, because you divided. Thats where you went wrong.
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