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Homework Help: Planetary motion the mass of the sun

  1. Oct 29, 2007 #1
    1. The problem statement, all variables and given/known data

    Derive the equation using Newton's Law of gravitation and the equation for circular motion.

    2. Relevant equations

    V = [tex]\sqrt{\stackrel{GM}{r}}[/tex]

    Where G is the universal gravitational constant, M is the mass of the central body and r is the radius of the orbit

    3. The attempt at a solution

    F= GM1*m2/r2

    F= GMp*Ms/r2

    Fc= MpV2/r


    GMpMS/r2 = mpV2/r

    I'm not sure how to derive this equation ???
  2. jcsd
  3. Oct 29, 2007 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    Your heading in the right direction, now all you do is re-arrange the last equation until you've solved for V. (hint: some of the variables at least partially cancel out.)
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