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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 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 re-definition of the kilogram and several other units came into effect on 20 May 2019, following a final vote by the CGPM in November 2018. [4] The new definition uses only invariant quantities of nature: the speed of light, the caesium hyperfine frequency, the Planck constant and the elementary charge. [5]
[citation needed] The kilogram-force is equal to the magnitude of the force exerted on one kilogram of mass in a 9.806 65 m/s 2 gravitational field (standard gravity, a conventional value approximating the average magnitude of gravity on Earth). [2] That is, it is the weight of a kilogram under standard gravity. One kilogram-force is defined as ...
For example, in retail commerce, the "net weight" of products actually refers to mass, and is expressed in mass units such as grams or ounces (see also Pound: Use in commerce). Conversely, the load index rating on automobile tires, which specifies the maximum structural load for a tire in kilograms, refers to weight; that is, the force due to ...
Scientists want to define the kilogram by gravity—and not just electricity. Here’s why correctly quantifying mass is more important than you think.
For example, an object with a mass of one kilogram has a weight of about 9.8 newtons on the surface of the Earth, and about one-sixth as much on the Moon. Although weight and mass are scientifically distinct quantities, the terms are often confused with each other in everyday use (e.g. comparing and converting force weight in pounds to mass in ...
This article consists of tables outlining a number of physical quantities.. The first table lists the fundamental quantities used in the International System of Units to define the physical dimension of physical quantities for dimensional analysis.