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This is the definition declared in the modern International System of Units in 1960. [13] The definition of the joule as J = kg⋅m 2 ⋅s −2 has remained unchanged since 1946, but the joule as a derived unit has inherited changes in the definitions of the second (in 1960 and 1967), the metre (in 1983) and the kilogram . [14]
Energy is defined via work, so the SI unit of energy is the same as the unit of work – the joule (J), named in honour of James Prescott Joule [1] and his experiments on the mechanical equivalent of heat. In slightly more fundamental terms, 1 joule is equal to 1 newton metre and, in terms of SI base units
The SI unit of kinetic energy is the joule, while the English unit of kinetic energy is the foot-pound. In relativistic mechanics , 1 2 m v 2 {\textstyle {\frac {1}{2}}mv^{2}} is a good approximation of kinetic energy only when v is much less than the speed of light .
The joule is named after James Prescott Joule. As with every SI unit named for a person, its symbol starts with an upper case letter (J), but when written in full, it follows the rules for capitalisation of a common noun; i.e., joule becomes capitalised at the beginning of a sentence and in titles but is otherwise in lower case.
Thus, one joule is one watt-second, and 3600 joules equal one watt-hour. The CGS energy unit is the erg and the imperial and US customary unit is the foot pound . Other energy units such as the electronvolt , food calorie or thermodynamic kcal (based on the temperature change of water in a heating process), and BTU are used in specific areas of ...
Illinois Gov. J.B. Pritzker is renaming Lake Michigan to “Lake Illinois," poking fun at President Donald Trump’s recent executive order where he changed the Gulf of Mexico to Gulf of America.
1 therm is defined in the United States as 100,000 Btu using the Btu 59 °F definition. In the EU it was listed in 1979 with the BTU IT definition and planned to be discarded as a legal unit of trade by 1994. [21] United Kingdom regulations were amended to replace therms with joules with effect from 1 January 2000. [22]
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