|Mechanics (Greek, â€˜about contrivancesâ€™), in physics, has come to have a multitude of meanings. Its original definition was the study of systems under the action of forces. Today there are different types of mechanics which pertain to different systems.
The most familiar form of mechanics is Newtonian mechanics. This is a description of the physical principles underlying force, mass and motion that holds for all â€˜classicalâ€™ systems. Classical systems are those where the scale of the system is too large to make quantum effects noticeable, and the velocity of the system is far less than that of light, making relativistic effects negligible. (Quantum effects can be seen at about 1/1000 of a millimetre, and the speed of light is about 186,000 miles per second.) Thus all familiar systems are covered by Newtonian mechanics. Specializations within Newtonian mechanics include statics, dynamics, fluid mechanics, celestial mechanics and many others.
Quantum mechanics is one of the great achievements of the 20th century. The work of SchrÃ¶dinger and Heisenberg laid the foundations for this science, upon which all modern computers, electronics, optical communications and other small-scale processes depend.
At the other end of the scale we have relativistic mechanics. This is based on the work of Einstein in the early part of the century, and applies to objects travelling at an appreciable fraction of the velocity of light, or objects subjected to enormous gravities.
See also quantization; quantum theory; relativity.