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Why are the units of work and energy same?


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May 24, 2009 10:16AM

Work and Energy have the same unit because they are intimately related by the Work-Energy Theorem. This states that the Work done on an object moving from point A to point B is the difference in the Kinetic Energy it has at the two points. In simplified form it says that in order to do Work, you must use Energy; you can never do Work without using Energy, and so for convenience we give them the same unit. You didn't ask about Heat, but it really ought to be mentioned here, too; when you use Energy to do Work, some of the Energy usually gets converted to Heat by friction, so we can and do also use the same unit for Heat. Work and Energy and Heat are not the same thing, but they are inextricably related. By extension, the Theorem lets us define forms of Energy other than Kinetic Energy which enable us to do Work: Chemical Energy, Electrical Energy, Nuclear Energy, Gravitational Energy, etc. The SI unit of work or energy is Newton-meter (Nm). Another name for it is Joule (J). 1 joule is defined as the work done when a force of one newton acts over one metre of distance. 1 joule is also the amount of heat dissipated when a current of 1 ampere passes through a resistor of 1 ohm for 1 second (or 1 watt-second). Please use the following link to confirm the accuracy of the information presented here, or for more information.