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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").
The International Prototype of the Kilogram (referred to by metrologists as the IPK or Le Grand K; sometimes called the ur-kilogram, [1] [2] or urkilogram, [3] particularly by German-language authors writing in English [3] [4]:30 [5]: 64 ) is an object whose mass was used to define the kilogram from 1889, when it replaced the Kilogramme des ...
Template: Units of force. 16 languages ... Download as PDF; Printable version; ... as used in the official definition of the kilogram-force is used here for all ...
The base units are defined in terms of the defining constants. For example, the kilogram is defined by taking the Planck constant h to be 6.626 070 15 × 10 −34 J⋅s, giving the expression in terms of the defining constants [1]: 131 1 kg = (299 792 458) 2 / (6.626 070 15 × 10 −34)(9 192 631 770) h Δν Cs / c 2 .
The redefinition of the kilogram relied on a concept known as the quantum metrological triangle, which redefines quantum effects in terms of h (the Planck constant) and e (the elementary charge.)
The quantity proportional to the number of particles in a sample, with the Avogadro constant as the proportionality constant: mole (mol) N: extensive, scalar Luminous intensity: I v: Wavelength-weighted power of emitted light per unit solid angle: candela (cd) J: scalar
For example, the atomic mass constant is exactly known when expressed using the dalton (its value is exactly 1 Da), but the kilogram is not exactly known when using these units, the opposite of when expressing the same quantities using the kilogram.
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 .