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The 10th CGPM in 1954 resolved to create an international system of units [31]: 41 and in 1960, the 11th CGPM adopted the International System of Units, abbreviated SI from the French name Le Système international d'unités, which included a specification for units of measurement. [5]: 110
"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 ∆ν Cs." [1] The mass of one litre of water at the temperature ...
the electronvolt (eV), a unit of energy, used to express mass in units of eV/c 2 through mass–energy equivalence; the dalton (Da), equal to 1/12 of the mass of a free carbon-12 atom, approximately 1.66 × 10 −27 kg. [note 2] Outside the SI system, other units of mass include: the slug (sl), an Imperial unit of mass (about 14.6 kg)
The unit of time should be the second; the unit of length should be either the metre or a decimal multiple of it; and the unit of mass should be the gram or a decimal multiple of it. Metric systems have evolved since the 1790s, as science and technology have evolved, in providing a single universal measuring system.
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 tonne (t) is an SI-compatible unit of mass equal to a megagram (Mg), or 10 3 kg.
This was an official unit of measurement in South Africa until the 1970s, and was defined in November 2007 by the South African Law Society as having a conversion factor of 1 morgen = 0.856 532 hectares. [27] This unit of measure was also used in the Dutch colonial province of New Netherland (later New York and parts of New England). [28] [29]
The other units of length and mass, and all units of area, volume, and derived units such as density were derived from these two base units. Mesures usuelles ( French for customary measures ) were a system of measurement introduced as a compromise between the metric system and traditional measurements.
With this instrument, the measurement of mass is no longer dependent on a defined mass standard and is instead dependent on natural physical constants. Metrology is the scientific study of measurement. [1] It establishes a common understanding of units, crucial in linking human activities. [2]