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relativity

(Encyclopedia)relativity, physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference. One consequ...

Newton's laws of motion

(Encyclopedia)Newton's laws of motion: see motion. ...

motion

(Encyclopedia)motion, the change of position of one body with respect to another. The rate of change is the speed of the body. If the direction of motion is also given, then the velocity of the body is determined; ...

perpetual-motion machine

(Encyclopedia)perpetual-motion machine, device that would be able to operate continuously and supply useful work, in violation of the laws of thermodynamics. A machine that would produce more energy in the form of ...

Kepler's laws

(Encyclopedia)CE5 Schematic representation of Kepler's second law: The areas ABF and A′B′F′ are equal and are swept out in equal intervals of time by a planet orbiting around the sun (at F). Kepler's laws...

conservation laws

(Encyclopedia)conservation laws, in physics, basic laws that together determine which processes can or cannot occur in nature; each law maintains that the total value of the quantity governed by that law, e.g., mas...

time and motion study

(Encyclopedia)time and motion study, analysis of the operations required to produce a manufactured article in a factory, with the aim of increasing efficiency. Each operation is studied minutely and analyzed in ord...

conflict of laws

(Encyclopedia)conflict of laws, that part of the law in each state, country, or other jurisdiction that determines whether, in dealing with a particular legal situation, its law or the law of some other jurisdictio...

proper motion

(Encyclopedia)proper motion, in astronomy, apparent movement of a star on the celestial sphere, usually measured as seconds of arc per year; it is due both to the actual relative motions of the sun and the star thr...

war, laws of

(Encyclopedia)war, laws of, in international law, rules and principles regulating an armed conflict between nations. These laws are designed to minimize the destruction of life and property, to proscribe cruel trea...