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Homework Help: Gravitational forces

  1. Apr 2, 2005 #1
    When in orbit, a communication satellite attracts the earth with a force of F and the earth-satellite gravitational potential energy (relative to zero at infinite separation) is - U. The radius of earth is assumed to be r.

    How do I find the satellite's altitude above the earth's surface and the mass of the satellite?
  2. jcsd
  3. Apr 2, 2005 #2


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    Obtain an expression for r²/m from the gravitation law of force between the earth and your satellite, and obtain an expression for r/m from the potential energy of the system. Plug the two expressions together.

    I found r = -U/F and m = U²/FGM

    (meaning [itex]r= \nabla F/F[/itex].. kinda cool.)
    Last edited: Apr 2, 2005
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