# Definition of Energy

#### Hyperreality

Is there an universal and complete definition for energy? Or has energy already being defined by the Principle of Conservation of Energy?

Energy cannot be created nor destroyed

We know that energy can be transformed from one form to another, but a force has to be applied to change the form of energy. e.g. When a man lifts a brick, the chemical energy possessed by the man is transformed into potential energy, and the transformation is caused by the force applied on the brick exerted by the man.

I am confused of which comes, because neither force or energy can exist beforehand of one another. (Energy transfoms to other forms because of force, but the existence force and its magnitude is also dependent on the amount of energy).

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#### eNtRopY

Energy is the ability to do work.

#### Hyperreality

Energy is the ability to do work.
Yes. But gives energy the ability to do work?

#### steppenwolf

Originally posted by Hyperreality
Yes. But gives energy the ability to do work?
its definiton i think
but really, energy doesn't have the ability to do work, it is the ability to do work.

#### RuroumiKenshin

I've also had trouble with the definition of energy. What about the "E" in e=mc2?
and mystic energy (i never understood that; my mind is polluted with the energy in physics!)

#### drag

Greetings !
Originally posted by Hyperreality
Is there an universal and complete definition for energy?
Yep. It's a parameter used in physical
equations...
(Or like some one here said - the measure of the
ability to do work.)

Live long and prosper.

Staff Emeritus
Gold Member
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Like you want to do some work, say, to lift a stone, and you find it takes effort. This is caveman physics.

More advanced. You multiply the mass of the stone by the distance it was lifted. This gives you a measure of the work required. Then you conceive that in doing the work you expended some quantity of something. Call that something energy, and the quantity of energy expended is set exactly equal to the amount of work done. This is Renaissance physics.

Once you have the idea of energy as what you have to expend in order to do work, you can do all sorts of things with it. You can talk about relativistic energy and quantum energy and the law of conservation of (mass&) energy.

#### Loren Booda

Energy is equivalent to accelerating a mass over a distance, or the potential ability to do so.

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