# conservation of energy

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## Conservation of energy

The principle of conservation of energy states that energy cannot be created or destroyed, although it can be changed from one form to another. Thus in any isolated or closed system, the sum of all forms of energy remains constant. The energy of the system may be interconverted among many different forms—mechanical, electrical, magnetic, thermal, chemical, nuclear, and so on—and as time progresses, it tends to become less and less available; but within the limits of small experimental uncertainty, no change in total amount of energy has been observed in any situation in which it has been possible to ensure that energy has not entered or left the system in the form of work or heat. For a system that is both gaining and losing energy in the form of work and heat, as is true of any machine in operation, the energy principle asserts that the net gain of energy is equal to the total change of the system's internal energy. See Thermodynamic principles

There are many ways in which the principle of conservation of energy may be stated, depending on the intended application. Of particular interest is the special form of the principle known as the principle of conservation of mechanical energy which states that the mechanical energy of any system of bodies connected together in any way is conserved, provided that the system is free of all frictional forces, including internal friction that could arise during collisions of the bodies of the system.

J. P. Joule and others demonstrated the equivalence of heat and work by showing experimentally that for every definite amount of work done against friction there always appears a definite quantity of heat. The experiments usually were so arranged that the heat generated was absorbed by a given quantity of water, and it was observed that a given expenditure of mechanical energy always produced the same rise of temperature in the water. The resulting numerical relation between quantities of mechanical energy and heat is called the Joule equivalent, or is also known as mechanical equivalent of heat.

In view of the principle of equivalence of mass and energy in the restricted theory of relativity, the classical principle of conservation of energy must be regarded as a special case of the principle of conservation of mass-energy. However, this more general principle need be invoked only when dealing with certain nuclear phenomena or when speeds comparable with the speed of light (1.86 × 105 mi/s or 3 × 108 m/s) are involved.

## conservation of energy

[‚kän·sər′vā·shən əv ′en·ər·jē]
(physics)
The principle that energy cannot be created or destroyed, although it can be changed from one form to another; no violation of this principle has been found. Also known as energy conservation.
References in periodicals archive ?
3 Deriving the original Newton's second law by using the law of conservation of energy
p] denotes the value given by the law of conservation of energy.
Now we calculate the related quantities according to the law of conservation of energy.
P], then we should have: l = l/D', and D-I = (D/D')-1; these two equations all give: D'= 1, this means that for free falling problem, by using the law of conservation of energy, we strictly derive the original Newton's second law F = ma.
The height of the bar remains constant representing the application of the law of conservation of energy.
In the calculation they are using the law of conservation of energy at least intuitively.
In each case, the law of conservation of energy is invoked to determine missing components.
1) The First Law: The law of conservation of energy has a number of titles including the First Law of Thermodynamics.
Firstly, through "universal relations", the variational principles established by the law of conservation of energy can be given with least squares method (LSM).
The above-mentioned principles are established by using the law of conservation of energy directly.
5) and (6), as Q is the result calculated with the law of conservation of energy, it gives the variational principle established by using the law of conservation of energy indirectly.
11)) and the law of conservation of energy, all the related quantities can be calculated, then substitute them into Eq.

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