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Homework Help: Gravitational acceleration above the Earth's surface

  1. Nov 8, 2006 #1
    At what altitude above the Earth's surface would the gravitational acceleration be 4.9 m/s^2?

    I thought this what very simple but apparently it is not since I got the wrong answer and can't figure out what I did wrong.
    I used g= GM/r^2= GM/(R+h)^2 R being radius of earth and h being the altitude.

    g= 4.9m/s^2

    4.9= (6.73e-11)(5.98e24)/(6.37e6+ h)^2
    4.9= 3.99e14-(6.37e6+h)^2
    solved for h and got 2.00e7m

    Can someone tell me where I went wrong? Thanks
  2. jcsd
  3. Nov 8, 2006 #2


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    The approach is OK, but the computation has an error. You really only need the radius of the earth and g at the surface to do this, but your approach is OK too.

    9.8m/s^2 = GM/R^2
    4.9m/s^2 = GM/(R+h)^2
    2 = (R+h)^2/R^2 <== dividing 1st eq by 2nd eq
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