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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 joule-second also appears in quantum mechanics within the definition of the Planck constant. [2] Angular momentum is the product of an object's moment of inertia, in units of kg⋅m 2 and its angular velocity in units of rad⋅s −1. This product of moment of inertia and angular velocity yields kg⋅m 2 ⋅s −1 or the joule-second.
L 2 T −3: Action: S: Momentum of particle multiplied by distance travelled J/Hz L 2 M T −1: scalar Angular acceleration: ω a: Change in angular velocity per unit time rad/s 2: T −2: Area: A: Extent of a surface m 2: L 2: extensive, bivector or scalar Area density: ρ A: Mass per unit area kg⋅m −2: L −2 M: intensive Capacitance: C ...
Symbol Meaning SI unit of measure magnetic vector potential: tesla meter (T⋅m) area: square meter (m 2) amplitude: meter: atomic mass number: unitless acceleration: meter per second squared (m/s 2) magnetic flux density
In physics and chemistry, the word calorie and its symbol usually refer to the small unit, the large one being called kilocalorie (kcal). However, the kcal is not officially part of the International System of Units (SI), and is regarded as obsolete, [ 2 ] having been replaced in many uses by the SI derived unit of energy , the joule (J), [ 9 ...
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.
Kinetic energy per unit mass: 1 / 2 v 2, where v is the speed (giving J/kg when v is in m/s). See also kinetic energy per unit mass of projectiles . Potential energy with respect to gravity, close to Earth, per unit mass: gh , where g is the acceleration due to gravity ( standardized as ≈9.8 m/s 2 ) and h is the height above the ...