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SI: Physics: Basic: metre: m: L: length: The distance travelled by light in vacuum in 1 / 299 792 458 second. m: SI: Physics: Basic: kilogram [n 2] kg: M: mass: The kilogram is defined by setting the Planck constant h exactly to 6.626 070 15 × 10 −34 J⋅s (J = kg⋅m 2 ⋅s −2), given the definitions of the metre and the second ...
The kilogram (also spelled kilogramme [1]) is the base unit of mass in the International System of Units (SI), having the unit symbol kg. [1] The word "kilogram" is formed from the combination of the metric prefix kilo- (meaning one thousand) and gram ; [ 2 ] it is colloquially shortened to " kilo " (plural "kilos").
2019 definition: The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 × 10 −34 when expressed in the unit J ⋅s, which is equal to kg⋅m 2 ⋅s −1 , where the metre and the second are defined in terms of c and Δ ν Cs .
The kelvin is defined by setting the fixed numerical value of the Boltzmann constant k to 1.380 649 × 10 −23 J⋅K −1, (J = kg⋅m 2 ⋅s −2), given the definition of the kilogram, the metre, and the second. mole: mol amount of substance: The amount of substance of 6.022 140 76 × 10 23 elementary entities.
The SI system after 1983, but before the 2019 revision: Dependence of base unit definitions on other base units (for example, the metre is defined as the distance travelled by light in a specific fraction of a second), with the constants of nature and artefacts used to define them (such as the mass of the IPK for the kilogram). New SI ...
The SI system has been adopted as the official system of weights and measures by most countries in the world. A notable outlier is the United States (US). Although used in some contexts, the US has resisted full adoption; continuing to use "a conglomeration of basically incoherent measurement systems". [2]
The kilogram is the only standard unit to include an SI prefix (kilo-) as part of its name. The gram (10 −3 kg) is an SI derived unit of mass. However, the names of all SI mass units are based on gram, rather than on kilogram; thus 10 3 kg is a megagram (10 6 g), not a *kilokilogram.
The SI base unit of mass is the kilogram (kg). In physics, mass is not the same as weight, even though mass is often determined by measuring the object's weight using a spring scale, rather than balance scale comparing it directly with known masses. An object on the Moon would weigh less than it does on Earth because of the lower gravity, but ...