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Homework Help: Gravitation Field Question

  1. Dec 4, 2006 #1
    I just want to know if there is enough information for me to answer this question.. to me it just seems like i should be given some more information

    A satellite is designed to orbit Earth at an altitude above its surface that will place it in a gravitational field with a strength 4.5 N/kg

    Calculate the distance above the surface of Earth at which the satellite must orbit.

    Given :
    Me = 5.98 x 10^24
    Radius of earth = 6.38 x10 ^6 km or 6.38 x 10^9 m
    radius of satellite (r2) = RofE + X

    it just seems like i should have the mass of the satellite to answer this question, can someone tell me if i have enough to solve it?
  2. jcsd
  3. Dec 4, 2006 #2
    The gravitational field strength is given by:

    [tex] g = \frac{GM_{E}}{r^{2}} [/tex]

    So you have [tex] 4.5 = \frac{G(5.98\times10^{24})}{(R_{E}+X)^{2}} [/tex] and solve for X.
    Last edited: Dec 4, 2006
  4. Dec 4, 2006 #3
    thank you..
  5. Dec 4, 2006 #4
    ok.. im working this out and im getting totally confused again
    can someone show me how to isolate x in this equation?
  6. Dec 5, 2006 #5
    Can someone tell me if this is right?
    (Radius Earth + X)^2 = G(Mass earth)/ 4.5

    or X = (Sqrt (G(Mass earth)/ 4.5)) - Radius Earth??
  7. Dec 5, 2006 #6


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    looks ok to me
  8. Dec 5, 2006 #7
    Thank you thank you thank you
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