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| Version | Summary | Created by | Modification | Content Size | Created at | Operation |
|---|---|---|---|---|---|---|
| 1 | Dean Liu | -- | 1920 | 2022-11-25 01:41:48 |
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In physics, action is a numerical value describing how a physical system has changed over time. Action is significant because the equations of motion of the system can be derived through the principle of stationary action. In the simple case of a single particle moving with a specified velocity, the action is the momentum of the particle times the distance it moves, added up along its path, or equivalently, twice its kinetic energy times the length of time for which it has that amount of energy, added up over the period of time under consideration. For more complicated systems, all such quantities are added together. More formally, action is a mathematical functional which takes the trajectory, also called path or history, of the system as its argument and has a real number as its result. Generally, the action takes different values for different paths. Action has dimensions of energy × time or momentum × length, and its SI unit is joule-second (like the Planck constant h).
References
- Quantum Mechanics, E. Abers, Pearson Ed., Addison Wesley, Prentice Hall Inc, 2004, ISBN:978-0-13-146100-0
- Analytical Mechanics, L.N. Hand, J.D. Finch, Cambridge University Press, 2008, ISBN:978-0-521-57572-0
- Œuvres de Mr de Maupertuis (pre-1801 Imprint Collection at the Library of Congress).
- Encyclopaedia of Physics (2nd Edition), R.G. Lerner, G.L. Trigg, VHC publishers, 1991, ISBN:3-527-26954-1 (Verlagsgesellschaft), ISBN:0-89573-752-3 (VHC Inc.)
- The Road to Reality, Roger Penrose, Vintage books, 2007, ISBN:0-679-77631-1
- T. W. B. Kibble, Classical Mechanics, European Physics Series, McGraw-Hill (UK), 1973, ISBN:0-07-084018-0
- L. D. Landau and E. M. Lifshitz (1971). The Classical Theory of Fields. Addison-Wesley. Sec. 8. p. 24–25.
