«Units with special names and symbols; units that incorporate special names and symbols». International Bureau of Weights and Measures. Arxivat de l'original el 28 juny 2009. [Consulta: 18 març 2015]. «A derived unit can often be expressed in different ways by combining base units with derived units having special names. Joule, for example, may formally be written newton metre, or kilogram metre squared per second squared. This, however, is an algebraic freedom to be governed by common sense physical considerations; in a given situation some forms may be more helpful than others. In practice, with certain quantities, preference is given to the use of certain special unit names, or combinations of unit names, to facilitate the distinction between different quantities having the same dimension.»
(anglès)Definició del joule a lloc web SizesThe joule was adopted in 1889 by the International Electrical Congress. When the CGPM first defined SI, in 1960, it included the joule as one of the derived units.
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«Units with special names and symbols; units that incorporate special names and symbols». International Bureau of Weights and Measures. Arxivat de l'original el 28 juny 2009. [Consulta: 18 març 2015]. «A derived unit can often be expressed in different ways by combining base units with derived units having special names. Joule, for example, may formally be written newton metre, or kilogram metre squared per second squared. This, however, is an algebraic freedom to be governed by common sense physical considerations; in a given situation some forms may be more helpful than others. In practice, with certain quantities, preference is given to the use of certain special unit names, or combinations of unit names, to facilitate the distinction between different quantities having the same dimension.»
