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In physics, a force is said to do work if, when acting on a body, there is a displacement of the point of application in the direction of the force. For example, when a ball is held above the ground and then dropped, the work done on the ball as it falls is equal to the weight of the ball (a force) multiplied by the distance to the ground (a displacement). The term ''work'' was introduced in 1826 by the French mathematician Gaspard-Gustave Coriolis〔Coriolis, Gustave. (1829). ''Calculation of the Effect of Machines, or Considerations on the Use of Engines and their Evaluation'' (''Du Calcul de l'effet des Machines, ou Considérations sur l'emploi des Moteurs et sur Leur Evaluation''). Paris: Carilian-Goeury, Libraire.〕 as "weight ''lifted'' through a height", which is based on the use of early steam engines to lift buckets of water out of flooded ore mines. The SI unit of work is the newton-metre or joule (J). ==Units== The SI unit of work is the joule (J), which is defined as the work expended by a force of one newton through a distance of one metre. The dimensionally equivalent newton-metre (N⋅m) is sometimes used as the measuring unit for work, but this can be confused with the unit newton-metre, which is the measurement unit of torque. Usage of N⋅m is discouraged by the SI authority, since it can lead to confusion as to whether the quantity expressed in newton metres is a torque measurement, or a measurement of energy.〔http://www.bipm.org/en/si/si_brochure/chapter2/2-2/2-2-2.html〕 Non-SI units of work include the erg, the foot-pound, the foot-poundal, the kilowatt hour, the litre-atmosphere, and the horsepower-hour. Due to work having the same physical dimension as heat, occasionally measurement units typically reserved for heat or energy content, such as therm, BTU and Calorie, are utilized as a measuring unit. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Work (physics)」の詳細全文を読む スポンサード リンク
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