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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 ...
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 .
Scientists want to define the kilogram by gravity—and not just electricity. Here’s why correctly quantifying mass is more important than you think.
The SI base units, or Systéme International d'unités, consists of the metre, kilogram, second, ampere, kelvin, mole and candela. A unit multiple (or multiple of a unit) is an integer multiple of a given unit; likewise a unit submultiple (or submultiple of a unit) is a submultiple or a unit fraction of a given unit. [1]
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 ...
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 .
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.