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Homework Help: Determine the Altitude of a Satellite above Earth Given it's Constant Speed

  1. Mar 28, 2009 #1
    1. The problem statement, all variables and given/known data

    A remote-sensing satellite travels in a circular orbit at a constant speed of 8.2 x 10^3 m/s. Determing the altitude in kilometres of the satellite above Earth's surface.

    2. Relevant equations

    Fc = FG

    3. The attempt at a solution

    mv^2/r = GMm/r^2
    v^2 = GM/r
    r = GM/v^2
    r = (6.67 x 10^-11 * 5.98 x 10^24)/(8.2 x 10^3)^2
    r = 5931975 m - radius of Earth (6.38 x 10^6 m)

    Why am I getting a negative number? Is there a mistake in my conversions or am I completely off as to how to solve this? Any help will be greatly appreciated. :)
  2. jcsd
  3. Mar 28, 2009 #2


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    Homework Helper

    Using μ = G*M ≈ 400,000 (if you keep things in km), I get V2= 400,000/(8.2)2 = 5948 km.

    Maybe it's a fast earth worm?
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