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Gravitational potential energy negative?

  1. Mar 22, 2006 #1
    Can kinetic energy of a system or gravitational potential energy be negative?

    I am reading about the two but its very complex and cant seem to describe why.
  2. jcsd
  3. Mar 22, 2006 #2

    Doc Al

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    Staff: Mentor

    Kinetic energy must be positive, but gravitational PE can certainly be negative. Gravitational PE depends on what you choose as your (arbitrary) reference point, where you define PE = 0. (Only changes in PE are physically significant.)
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