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Homework Help: Calculating orbital velocity

  1. Dec 22, 2012 #1
    1. The problem statement, all variables and given/known data

    If calculating the orbital velocity of an asteroid at perihelion I use:

    Vp = {GM/a ((1+e)/(1-e))}^0.5

    Is the G the gravitational constant G = 6.67x10^-11
    Is M the mass of the sun = 1.988x10^30 kg
    Is 'a' the mean distance of the asteroid from the Sun in metres/km/AU ?

    Thank you.

    2. Relevant equations

    3. The attempt at a solution
    Last edited: Dec 22, 2012
  2. jcsd
  3. Dec 22, 2012 #2


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    Staff: Mentor

    Choose meters if you want the result in m/s, and use M in kg and G in m3kg-1s-2. Otherwise you'll have to fiddle with the units of GM to match your choice if length unit.
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