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Free particle and some doubts

  1. Oct 22, 2011 #1
    1. The problem statement, all variables and given/known data

    Revered members,
    A free particle is one which has no forces acting on it and since there is no forces acting on it, so there is no potential energy and E is entirely kinetic.

    2. Relevant equations

    3. The attempt at a solution

    My doubt is, when no forces act on a particle, it should remain at rest and possess potential energy only and Kinetic energy should be zero. How the converse happens here?
  2. jcsd
  3. Oct 22, 2011 #2


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    Science Advisor

    I am not sure what it would mean to say that there is "no potential energy" since potential energy is relative- that is, given any situation, you can choose the potential energy to be whatever value you like at any one given point. However, your statement that "when no forces act on a particle, it should remain at rest" is not quite right. That is true only if the particle was initially at rest. If it initially has speed v (and so kinetic energy (1/2)mv^2) it will continue moving with that speed and kinetic energy. You can take the potential energy to be any constant.
  4. Oct 23, 2011 #3
    Thanks a lot HallsofIvy.
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