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Homework Help: Calculate the change in gravitational potential energy

  1. Oct 28, 2012 #1
    1. The problem statement, all variables and given/known data
    A satellite of mass 750kg is changed from an orbital radius of 7000000m to a geostationary orbit of 4.2*10^4. Calculate the change in its gravitational potential energy

    Mass= 750
    Earths radius= 6380000m
    Gravitational constant= 6.67*10^-11
    Earths mass=6*10^24

    2. Relevant equations

    So I am guessing I have to use this equation
    Final Gpe- initial Gpe
    (-GMm/r)-(-GMm/r)

    3. The attempt at a solution
    (-6.67*10^-11*750*6*10^24/(7000000+6380000))-(-6.67*10^-11*750*6*10^24/(4.2*10^4*10^3)
    = 1.69 *10^10

    The answer is 3.7*10^8
    I don't know where I went wrong?
     
  2. jcsd
  3. Oct 28, 2012 #2
    what is the new radius?
     
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