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Homework Help: Speed update of a comet in an ELLIPTICAL orbit

  1. Feb 18, 2010 #1
    A comet is in an elliptical orbit around the Sun. Its closest approach to the Sun is a distance of 5e10 m (inside the orbit of Mercury), at which point its speed is 9e4 m/s. Its farthest distance from the Sun is far beyond the orbit of Pluto. What is its speed when it is 6e12 m from the Sun? (This is the approximate distance of Pluto from the Sun.)

    2. Relevant equations
    Ug(r) = -G(m1*m2)/r
    this is a guess, the problem is i dont know what equations to use

    i tried to solve it with an incorrect method and got a speed of 3500 something m/s
  2. jcsd
  3. Feb 18, 2010 #2


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    Homework Helper

    Have you tried the conservation of energy?
  4. Feb 18, 2010 #3
    that's the problem, everyone says that and i have no idea what is needed equations are needed to figure that out what the conservation of energy is
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