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Homework Help: Universal Gravitation and magnitude

  1. Mar 5, 2008 #1
    1. The problem statement, all variables and given/known data
    Determine the magnitude of the force of gravity acting on a 340 kg satellite, 850km above Earth's surface.


    2. Relevant equations
    So I dedcided to use the Universal Gravitation Law:
    Fg = (Gm1m2)/d^2


    3. The attempt at a solution
    m1=5.98E24 (earth's mass)
    m2=340kg (satellite)
    G=6.67E-11
    d=850,000m

    After subbing them all into the formula I got 187,701N.
    However the answer in the book is 2.1E2N.
    So I'm not sure if I did it right... can you please check it?
    Thanks
     
  2. jcsd
  3. Mar 5, 2008 #2

    Doc Al

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    Staff: Mentor

    Good choice. But the distance "d" is between the centers of the two bodies, not height above the Earth's surface.
     
  4. Mar 5, 2008 #3
    Oh.. I see.
    So how can I continue? I'm not really sure what to do next...
     
  5. Mar 5, 2008 #4

    Doc Al

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    Staff: Mentor

    You're given the distance between the satellite and the Earth's surface. What's the distance from the Earth's surface to the Earth's center--the radius of the Earth? (Look it up!)
     
  6. Mar 5, 2008 #5
    Alright I understand.
    Thanks :)
     
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