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Homework Help: Physics Problem: Satellites in Circular Orbits

  1. Oct 3, 2004 #1
    A satellite orbits a planet at a distance of 3.70*10^8 m. Assume that this distance is between the centers of the planet and the satellite and that the mass of the planet is 3.93*10^24 kg. Find the period for the moon's motion around the earth. Express the answers in earth days.

    I tried using this equation: T= (2pi)(r)^(3/2) divided by square root of GMe
    The answer I got wasn't right. Please Help!!!
  2. jcsd
  3. Oct 3, 2004 #2
    I know this sounds like a lot of work but if your equations aren't working right and nobody else gives an answer (I'll delete this if someone does) you can just set centripetal force equal to the gravitational force between two bodies (the mass of the moon cancels out so you don't need it but put it in as a constant first) and solve for the velocity. This velocity can then be used to calculate the period. Edit I would like to point out if you pull this off you will have derived the equation you were told to use.
  4. Oct 3, 2004 #3
    Shawonna, show us your work using that formula, cuz it should work.
  5. Oct 3, 2004 #4
    Physics Problem: Satellites in Circular Orbits

    Here is my work:

    T= 2*pi*(3.70*10^8)^(3/2) DIVIDED BY (6.67*10^-11)*(3.93*10^24)

    i keep getting the wrong answer.
  6. Oct 3, 2004 #5
    U sure the formula is right??
    i have this feeling u missed a root somewhere
    prolly sqrt(G)??

    -- AI
  7. Oct 3, 2004 #6
    I think Tenali is right. I don't see sqrt() in any of your work.
  8. Oct 3, 2004 #7


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    If you used the formula correctly, you should have got an answer in the order of 32 days.
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