Action (physics)

In physics, the action principle is an assertion about the nature of motion, from which the trajectory of an object subject to forces can be determined. The path of an object is the one that yields a stationary value for a quantity called the action.

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Thus, instead of thinking about an object accelerating in response to applied forces, one might think of them picking out the path with a stationary action.

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The principle is also called the principle of stationary action and also Hamilton's principle. Other statements of the principle include the less general and in fact incorrect principle of least action and the principle of minimal action.

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The action is a scalar (a number) with the unit of measure for Action as Energy × Time. The principle is a simple, general, and powerful theory for predicting motion in classical mechanics.

Related Topics:
Scalar - Unit of measure - Classical mechanics

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Extensions of the action principle describe relativistic mechanics, quantum mechanics, electricity and magnetism.

Related Topics:
Relativistic mechanics - Quantum mechanics

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