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Universal and Gravitational Force

  1. Feb 3, 2005 #1
    i have a couple questions to ask

    1: When a satellite is in eclipsical orbit, the total energy should stay the same wether it is at Perigee or Apogee, neglicting friction, correct?

    2: Which is larger - The total energy of the 2.00kg satellite in its 160km orbit or the total energy is its 144km orbit. Why the two answers are different?
  2. jcsd
  3. Feb 4, 2005 #2


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    1: Pretty much, It depends on how eliptical the orbit is.
    2: Well, of course the 160 km orbit, because earth's pull is weaker.
  4. Feb 4, 2005 #3

    Doc Al

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    Staff: Mentor

    That is correct. Total energy (KE + PE) is constant.

    The satellite in higher orbit has greater energy. To understand why, figure it out! Assume a circular orbit: use Newton's 2nd law for centripetal motion to find the speed and thus the KE. The PE = [itex]-GMm/r[/itex]. Now find the total energy for both orbits and compare.
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