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Homework Help: Physics Gravitational Force Question

  1. Jan 3, 2006 #1
    At a distance H above the surface of a plane, the true weight of a remote probe is one percent less than its true weight on the surface. The radius of the planet is R. Find the ratio H/R.

    Let Mp be mass of planet and Ms be the mass of space probe

    (true weight) Ft = GMpM/(r+h)^2

    (surface weight) Fs = GMpM/r^2

    Ft = GMpMs/r^2 - GMpMs/r^2(0.01)

    Ft = GMpMs/r^2 - GMpMs/r^2(0.01) = GMpMs/(r+h)^2

    i don't know where to go from here

    thanks in advance.
  2. jcsd
  3. Jan 3, 2006 #2


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    Homework Helper

    Multiply both sides by [itex]r^2[/itex] and write

    [tex]\frac {r^2}{(r+h)^2}[/tex]


    [tex]\frac {1}{\left(1 + \frac {h}{r}\right)^2}[/tex]

    You should be able to handle the rest.
  4. Jan 3, 2006 #3
    thank you very much for your help
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