gravity, centre of

Imaginary point where the total weight of a material body may be thought to be concentrated.

Since weight and mass are proportional, the same point may also be called the centre of mass, but the centre of mass does not require a gravitational field. A body's centre of gravity may coincide with its geometric centre, especially if the body is symmetric and composed of homogeneous material. In asymmetric, unhomogeneous, or hollow objects, the centre of gravity may be at some distance from the geometric centre or even at a point in space external to the object, such as between the legs of a chair.

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      in physics, imaginary point in a body of matter where, for convenience in certain calculations, the total weight of the body may be thought to be concentrated. The concept is sometimes useful in designing static structures (e.g., buildings and bridges) or in predicting the behaviour of a moving body when it is acted on by gravity.

      In a uniform gravitational field the centre of gravity is identical to the centre of mass, a term preferred by physicists. The two do not always coincide, however. For example, the Moon's (Moon) centre of mass is very close to its geometric centre (it is not exact because the Moon is not a perfect uniform sphere), but its centre of gravity is slightly displaced toward the Earth because of the stronger gravitational force on the Moon's near side.

      The location of a body's centre of gravity may coincide with the geometric centre of the body, especially in a symmetrically shaped object composed of homogeneous material. An asymmetrical object composed of a variety of materials with different masses, however, is likely to have a centre of gravity located at some distance from its geometric centre. In some cases, such as hollow bodies or irregularly shaped objects, the centre of gravity (or centre of mass) may occur in space at a point external to the physical material—e.g., in the centre of a tennis ball or between the legs of a chair.

 Published tables and handbooks list the centres of gravity for most common geometric shapes. For a triangular metal plate such as that depicted in the figure—>, the calculation would involve a summation of the moments of the weights of all the particles that make up the metal plate about point A. By equating this sum to the plate's weight W, multiplied by the unknown distance from the centre of gravity G to AC, the position of G relative to AC can be determined. The summation of the moments can be obtained easily and precisely by means of integral calculus.

      The centre of gravity of any body can also be determined by a simple physical procedure. When an object is suspended from any single point, its centre of gravity lies directly beneath that point.

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Universalium. 2010.

Look at other dictionaries:

  • centre of gravity — noun the point within something at which gravity can be considered to act; in uniform gravity it is equal to the center of mass • Syn: ↑center of gravity • Hypernyms: ↑center, ↑centre, ↑midpoint • Hyponyms: ↑center of flotation, ↑ …   Useful english dictionary

  • centre — n. & v. (US center) n. 1 the middle point, esp. of a line, circle, or sphere, equidistant from the ends or from any point on the circumference or surface. 2 a pivot or axis of rotation. 3 a a place or group of buildings forming a central point in …   Useful english dictionary

  • gravity — grav|i|ty [ˈgrævıti] n [U] [Date: 1400 1500; : French; Origin: gravité, from Latin gravitas, from gravis; GRAVE1] 1.) technical the force that causes something to fall to the ground or to be attracted to another ↑planet →↑gravitation ▪ the force… …   Dictionary of contemporary English

  • centre of flotation — noun the center of gravity of a floating object • Syn: ↑center of flotation • Hypernyms: ↑center of gravity, ↑centre of gravity …   Useful english dictionary

  • centre — /sen teuhr/, n., v., centred, centring. Chiefly Brit. center. * * * (as used in expressions) gravity centre of Pompidou Centre Beaubourg Centre community centre shopping centre * * * ▪ county, Pennsylvania, United States       county, central… …   Universalium

  • centre — 1. noun /ˈsɛntə,ˈsɛntɚ/ a) The point on a line that is midway between the ends. shopping centre b) The point in the interior of a circle that is equidistant from all points on the circumference of the circle …   Wiktionary

  • centre of gravity — n [singular] the point in any object on which it can balance …   Dictionary of contemporary English

  • centre of gravity — ► NOUN ▪ the point from which the weight of a body appears to act …   English terms dictionary

  • centre of attraction — The point to which bodies tend by the force of gravity or the like • • • Main Entry: ↑centre …   Useful english dictionary

  • gravity — ► NOUN 1) the force that attracts a body towards the centre of the earth, or towards any other physical body having mass. 2) extreme importance or seriousness. 3) solemnity of manner. ORIGIN Latin gravitas weight, seriousness …   English terms dictionary

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