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# kinetic energy

the energy of a body or a system with respect to the motion of the body or of the particles in the system. Cf. potential energy.
[1865-70]

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Form of energy that an object has by reason of its motion.

The kind of motion may be translation (motion along a path from one place to another), rotation about an axis, vibration, or any combination of motions. The total kinetic energy of a body or system is equal to the sum of the kinetic energies resulting from each type of motion. The kinetic energy of an object depends on its mass and velocity. For instance, the amount of kinetic energy KE of an object in translational motion is equal to one-half the product of its mass m and the square of its velocity v, or KE = 12mv2, provided the speed is low relative to the speed of light. At higher speeds, relativity changes the relationship.

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form of energy that an object or a particle has by reason of its motion. If work, which transfers energy, is done on an object by applying a net force, the object speeds up and thereby gains kinetic energy. Kinetic energy is a property of a moving object or particle and depends not only on its motion but also on its mass. The kind of motion may be translation (or motion along a path from one place to another), rotation about an axis, vibration, or any combination of motions.

Translational kinetic energy of a body is equal to one-half the product of its mass, m, and the square of its velocity, v, or 1/2mv2.

This formula is valid only for low to relatively high speeds; for extremely high-speed particles it yields values that are too small. When the speed of an object approaches that of light (3 × 108 metres per second, or 186,000 miles per second), its mass increases, and the laws of relativity must be used. Relativistic kinetic energy is equal to the increase in the mass of a particle over that which it has at rest multiplied by the square of the speed of light.

The unit of energy in the metre-kilogram-second system is the joule. A two-kilogram mass (something weighing 4.4 pounds on Earth) moving at a speed of one metre per second (slightly more than two miles per hour) has a kinetic energy of one joule. In the centimetre-gram-second system the unit of energy is the erg, 10−7 joule, equivalent to the kinetic energy of a mosquito in flight. Other units of energy also are used, in specific contexts, such as the still smaller unit, the electron volt, on the atomic and subatomic scale.

For a rotating body, the moment of inertia, I, corresponds to mass, and the angular velocity (omega), ω, corresponds to linear, or translational, velocity. Accordingly, rotational kinetic energy is equal to one-half the product of the moment of inertia and the square of the angular velocity, or 1/22.

The total kinetic energy of a body or a system is equal to the sum of the kinetic energies resulting from each type of motion. See mechanics.

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Universalium. 2010.

### Look at other dictionaries:

• Kinetic energy —   Energy available as a result of motion that varies directly in proportion to an object s mass and the square of its velocity.   U.S. Dept. of Energy, Energy Information Administration s Energy Glossary …   Energy terms

• Kinetic Energy —   Energy available as a result of motion that varies directly in proportion to an object s mass and the square of its velocity …   Energy terms

• Kinetic energy — kinetic ki*net ic (k[i^]*n[e^]t [i^]k or k[ i]*n[e^]t [i^]k), a. [Gr. kinhtiko s, from kinei^n to move.] (Physics) Moving or causing motion; motory; active, as opposed to latent. [1913 Webster] {Kinetic energy}. See {Energy}, n. 4. [1913 Webster] …   The Collaborative International Dictionary of English

• kinetic energy — ► NOUN Physics ▪ energy which a body possesses by virtue of being in motion. Compare with POTENTIAL ENERGY(Cf. ↑potential energy) …   English terms dictionary

• kinetic energy — n energy associated with motion * * * energy of motion; equal to one half the mass of a body times the square of its velocity …   Medical dictionary

• kinetic energy — n. the energy of a body that results from its motion …   English World dictionary

• kinetic energy —  Kinetic Energy  Кинетическая энергия   Энергия, механической системы, зависящая от скоростей ее точек. Изменение кинетической энергии системы при ее перемещении из одного положения в другое происходит под действием приложенных к системе внешних… …   Толковый англо-русский словарь по нанотехнологии. - М.

• Kinetic energy — The kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its current velocity . Having gained this energy during its acceleration …   Wikipedia

• kinetic energy —   lit. the energy of motion or movement. In geography, most commonly applied to the energy of moving water e.g. a river energy is a function of the volume of water and the velocity it moves at as it converts the potential energy it has from being …   Geography glossary

• kinetic energy — N UNCOUNT In physics, kinetic energy is the energy that is produced when something moves. [TECHNICAL] …   English dictionary