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Homework Help: Can the kinetic energy of a system be negative?

  1. Nov 11, 2008 #1
    what about the gravitational potential energy of a system?

    1. The problem statement, all variables and given/known data

    2. Relevant equations
  2. jcsd
  3. Nov 11, 2008 #2
    Nope. Think of the formula for KE. Mass is never negative, and even if the velocity is negative, its squared so the negative sign goes away.

    Gravitational Potential can be negative depending on where you define your potential to be zero. But really, only changes in potential energy are relevant. Its only when the gravitational potential energy changes that the KE changes, a force is exerted, etc.
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