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Entropy and energy

  1. Dec 18, 2009 #1
    Hello all. I'm not... really sure if this is the best place to post this question, so I'm open to any and all recommendations.

    My question is: Why do things move away from high potential energy states and toward high kinetic energy states?

    My thoughts: I was thinking about entropy recently, and if I remember correctly, things move from an area of high concentration to an area of lower concentration because that's the statistically most likely thing to happen. I was wondering if there was something similar going on with energy and motion. Do things behave this way because it is most likely?
    Particularly I thought about how, in quantum physics, a quantum spring is most likely to be found at a position of high kinetic energy, as opposed to the classical spring which tends to spend most of its time in a high PE state.
  2. jcsd
  3. Dec 19, 2009 #2
    Yep! I think so. Energy and entropy are very much related.

    Things move away from high potential energy because of entropy...or more specifically, in order to maximize entropy. (Note: It also moves away from high kinetic energy states for that reason). And yeah, the reason it does so is because it's more statistically likely to be in that state.

    Where is the energy in an object when it's not stored solely as potential energy?

    Well, as a ball rolls down an incline for example, some of that energy stored in the object gets transferred to kinetic energy, or dissipated as thermal energy (heat)...distributing its energy so it's not concentrated.

    Basically, if you look at the whole system microscopically, the total energy of a system would be equally split among its available 'degrees of freedom'. If you were to add more 'degrees of freedom' to the system, some of the energy in that system will spread over to that new state.

    ...so it is like things moving from higher concentration to lower concentration.
    Last edited: Dec 19, 2009
  4. Dec 20, 2009 #3
    Edit: Oh, I misread your post.
    I think this is right. Kinetic energy offers more possibilities to randomize energy. That's why it's favoured for increasing entropy.
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