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#Introduction to the Major Laws of Physics

By Andrew Zimmerman Jones. Physics Expert

Andrew Zimmerman Jones, Physics Guide for About.com, has studied and written about physics since 1991. He holds a Physics degree from Wabash College with honors awards. You can find out more about his work - both in science writing and in other areas - at the following locations:

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Newton s Three Laws of Motion:

Sir Isaac Newton developed the Three Laws of Motion. which describe basic rules about how the motion of physical objects change. Newton was able to define the fundamental relationship between the acceleration of an object and the total forces acting upon it.

Law of Gravity:

Newton developed his Law of Gravity to explain the attractive force between a pair of masses. In the twentieth century, it became clear that this is not the whole story, as Einstein s theory of general relativity has provided a more comprehensive explanation for the phenomenon of gravity.

Still, Newton s law of gravity is an accurate low-energy approximation that works for most of the cases that you ll explore in physics.

Conservation of Mass-Energy:

The total energy in a closed or isolated system is constant, no matter what happens. Another law stated that the mass in an isolated system is constant. When Einstein discovered the relationship E mc 2 (in other words that mass was a manifestation of energy) the law was said to refer to the conservation of mass-energy. The total of both mass and energy is retained, although some may change forms.

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The ultimate example of this is a nuclear explosion, where mass transforms into energy.

Conservation of Momentum:

The total momentum in a closed or isolated system remains constant. An alternative of this is the law of conservation of angular momentum .

Laws of Thermodynamics:

The laws of thermodynamics are actually specific manifestations of the law of conservation of mass-energy as it relates to thermodynamic processes.

Electrostatic Laws:

Coulomb s law and Gauss s law are formulations of the relationship between electrically charged particles to create electrostatic force and electrostatic fields. The formulas, it turns out, parallel the laws of universal gravitation in structure. There also exist similar laws relating to magnetism and electromagnetism as a whole.

Invariance of the Speed of Light:

Einstein s major insight, which led him to the Theory of Relativity. was the realization that the speed of light in a vacuum is constant and is not measured differently for observers in different inertial frames of reference, unlike all other forms of motion. Some theoretical physicists have conjectured different variable speed of light (VSL) possibilities, but these are highly speculative. Most physicists believe that Einstein was right and the speed of light is constant.

Modern Physics Physical Laws:

In the realm of relativity and quantum mechanics. scientists have found that these laws still apply, although their interpretation requires some refinement to be applied, resulting in fields such as quantum electronics and quantum gravity. Care should be taken in applying them in these situations.