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Homework Help: Earth and Satellites

  1. Jan 25, 2010 #1
    1. The problem statement, all variables and given/known data

    A geosynchronous satellite is one that stays above the same point on the equator of the earth.
    Determine the height above the Earth's surface such a satellite must orbit and find it's speed.

    2. Relevant equations
    Fg = GM1M2/r^2
    3. The attempt at a solution

    I really don't know where to start, but I thought that maybe I could use the T1^2/R1^3 = T2^2/R2^3 Where T1 = The time period of the moon and T2 = is the time period of the satellite. I don't know if we're suppose to know the distance of the moon to the Earth. Someone please help. My teacher can't teach.
  2. jcsd
  3. Jan 25, 2010 #2

    Andrew Mason

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    Science Advisor
    Homework Helper

    Follow these four steps:

    1. What is the force (gravity) on a satellite of mass m at a distance r from the earth's centre?
    2. What is the (centripetal) acceleration of a satellite prescribing a circular orbit of radius r (ie. from the earth's centre)?
    3. How are 1 and 2 related?
    4. Now, suppose that the angular speed of the satellite is the same as the angular speed of the earth's rotation about its axis and solve for r. Then work out what that is in terms of distance from the surface of the earth.

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