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Homework Help: Universal Gravitation

  1. Oct 9, 2008 #1


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    At what center-to-center distance from the Earth would a 0.9 kg mass weigh 0.9 N?

    I used equation g = GM/r^2 to get an answer of 8.17 X 10^-6 which is incorrect.

    Am I using the correct formula? Thanks
  2. jcsd
  3. Oct 9, 2008 #2
    Well you know at this distance, F = m which implies a = 1.

    Therefore use your formula like this: 1 = GM/r^2

    G = 6.67E-11
    M = 5.98E24
    r = 6.37E6 + R
    Where R is the distance from the surface of the Earth.

    You are going to want your answer to be of an order of much, much greater than E-6
  4. Oct 9, 2008 #3


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    I got it. Thanks for your help.
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