Talk:Energy

I have a proposed new general definition for energy that can be derived from basic quantum theory. In any quantum system (thus, as far as we know, in the real world), energy can be shown to be the rate of computing that is going on in a system, expressed in terms of quantum computational operations per unit time; at least this is true if one defines operations in the right way. I work out the appropriate definitions in some of my research articles. However, this new computational interpretation of energy is not widely accepted (at least, not yet). Nevertheless I have found it helpful for my own understanding. -MikeFrank <mpf@cise.ufl.edu>

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If Energy is defined as the ability to do work, I don't think work can be considered as a form of energy. Work is the result of the application of energy, but is not a form of energy.

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In physics, work is a name to describe how much energy has gone in to a task. It is equal to force * distance and is measured in joules, so it definitely is a form of energy. -- sodium

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More precisely, work is the mechanical process whereby energy is transfered from one form to another. For example when force from a potential field is applied over a given distance, such that work, W, is applied to the body, the kinetic energy of the body increases by the amount W, while the potential energy decreases by the same amount (W). In this sense, work is not itself energy, but refers to the amount of energy that is transferred from one form to another.--Matt Stoker

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I've merged 'Work' into the 'Energy' article, and set a redirect. -- The Anome From the old Work/Talk page:

What about Angular Work done, ie Torque * angle swept out? -- Dweir

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First, can someone define p in

KE = ∫ v·dp

Is that momemtum? And, just to clarify, that integral covers the relativistic and non-relativistic cases?

Second, and much more important: I feel this article is not yet terribly useful for the non-physicists in the audience. Does anyone have any ideas about how to answer questions like

1. What is energy?
2. Why does the energy concept enter into our theories? (Is it "real"? Is it useful? Why should anyone care?)

As far as I've been able to gather, the first question is a pretty philosophical one, along the lines of "What is a force?", and has no commonly accepted answer. Nonetheless, attributing energy to various situations enhances and simplifies our theories, so the concept is accepted on pragmatic grounds.

Thus we arrive at the second question. From my limited perspective, it seems like the concept of energy is chiefly useful because it allows us to predict things across problem domains. For example, applying the idea of energy, we can predict how fast a particular resting body would be made to move if a particular amount of heat were completely transformed into motion in that body. Similarly, it allows us to predict how much heat might result from breaking particular chemical bonds.

Without the unifying measure of energy, these comparisons and conversions would be much harder. I don't suppose it would be accurate to say it would be impossible, though, would it? If there were no equations involving energy, would there still be some way to say how much heat is equivalent to how much motion of a particular body?

Any comments on the accuracy of this explanation? Any references to articles that might explain this more coherently?

A more in-depth historical analysis than is available through the "What does energy really mean?" link might be interesting as well.

-- Ryguasu

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I've revised the introduction again, mainly because I was uneasy about the connection between work and energy. After reading the Feynman reference, I feel that the previous summary

In physics, energy is defined as the ability to do work.

is either incorrect or unhelpful. (A little of each?) There is obviously a connection between work and energy, but I don't think it's quite that simple. I've tried to give an alternative explanation in the current revision.

I'm not sure that merging "energy" and "work" was ultimately productive.

Also, this definition was in the article:

One definition of work is applying a force through a distance. In the one-dimensional case, that is to say W = ∫ f(x) dx, where f(x) gives the amount of force being applied as a function of the distance moved.

I've modified it in the current revision to try to make the text flow better. As an aside, I think it is unhelpful to have an article that takes upon itself to explain what work is about explain only "one definition of work", instead of having a more general discussion.

I must admit, I'm not the most qualified to edit articles about physics. Nonetheless, the current state of the article is such that it really isn't very useful for the average Joe. I'm hoping that making a few changes might nudge it in the right direction. --Ryguasu 01:27 Nov 21, 2002 (UTC)