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What is the process in which energy changes?

  1. Apr 17, 2003 #1
    everyone know the law of conservation of energy. but it can change to another form of energy.

    but i don't know how energy change to another kind of energy? what is the process in between the change?
    do anybody have any idea? thank you.
  2. jcsd
  3. Apr 17, 2003 #2
    One way to look at it is to consider that different forms of energy describe different kinds of structural properties of some physical system. For example if your system is a macroscopic solid body then its kinetic energy is dependent on its mass and its velocity averaged on all its particles - the velocity of its center of mass. That is, its kinetik energy describes (VERY roughly) "how heavy it is and how fast it moves". It also has termic energy which is dependent on the averaged speeds of all its particles as seen from a center of mass reference system. That is, its termic enery describes (VERY roughly) how fast its constituent particles jiggle around. If you are interested in only one particle then that particle becomes your physical system. In this case you only have kintetic energy. In a sense, the same property that earlier contributed to termic energy now contributes only to kinetic energy just because we changed the physical system we are interested in. However this is NOT a case of energy transformation.

    We would have energy transformation for example if our physical system consisted of two solid bodies which collide (not perfectly elastic). After the collision the bodies will move slower and their temperatures will be slightly higher. Bleah! Isn't that statement so VERY imprecise... Much better is to say that a part of the kinetic energy transforms into termic energy. And yo know what's funny? When people reaized that boddies have less kinetic energy after a collision they allready had definitions for kinetic energy and potential energy: they helped at studying cannonballs and things like that. But they didn't have the notion of termic energy. So they just DEFINED termic energy in a way that keeps energy conserved.

    What is the "process" by which energy transforms into another form? Well in this case its called "collision". In general the answer is probably INTERACTION, but it's not really that relevant untill you master a couple of concrete examples were energy transforms.

    In conclusion different forms of energy describe different structural properties of physical systems. This allows one to think in more abstract terms and not look at the details every time. So energy transformation can be viewed as "modification of structure". In general the reason for such a modification can be called "interaction".

    But let me repeat. These general discussions tend to obscure ideas for beginers.
  4. Apr 18, 2003 #3
    like we speaking
    we use the chemical energy to oscllate the air
    than transfer to kinectic energy
    and also must consider the internel energy(the sum of kinectic enery
    and potential energies of the particle making up the system)
    something like that ....
    the law of conservatin of energy is not something derived from basic physics principle, it is a law based on countless experiment
  5. Apr 18, 2003 #4
    Re: how?

    First of all, let's understand what energy is.
    Energy is not something we touch, see, or feel, we can't even measure it !
    So what is the aim of studying it ?
    Well, energy makes the objects having it to also have certain marks, and we have been able to calculate the ammount of energy from the marks that show (for example, we can calculate kinetic energy by knowing its mark (speed).
    So always remember when thinking of energy, that what is conserved is not the marks of energy, but the actually hidden energy under it.
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