SI_units_NIST

SI_units_NIST - Essentials of the SI Base derived units...

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Return to Units home page Units Topics: Introduction Units Prefixes Outside Rules Background Units Bibliography Constants, Uncertainty home page SI base units The SI is founded on seven SI base units for seven base quantities assumed to be mutually independent, as given in Table 1. For detailed information on the SI base units, see Definitions of the SI base units and their Historical context . SI derived units Other quantities, called derived quantities , are defined in terms of the seven base quantities via a system of quantity equations. The SI derived units for these derived quantities are obtained from these equations and the seven SI base units. Examples of such SI derived units are given in Table 2, where it should be noted that the symbol 1 for quantities of dimension 1 such as mass fraction is generally omitted. Table 1. SI base units Base quantity Name Symbol SI base unit length meter m mass kilogram kg time second s electric current ampere A thermodynamic temperature kelvin K amount of substance mole mol luminous intensity candela cd Derived quantity Name Symbol Table 2. Examples of SI derived units SI derived unit area square meter m 2 volume cubic meter m 3 speed, velocity meter per second m/s Page 1 of 5 12/12/2007 http://physics.nist.gov/cuu/Units/units.html

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acceleration meter per second squared m/s 2 wave number reciprocal meter m -1 mass density kilogram per cubic meter kg/m 3 specific volume cubic meter per kilogram m 3 /kg current density ampere per square meter A/m 2 magnetic field strength ampere per meter A/m amount-of-substance concentration mole per cubic meter mol/m 3 luminance candela per square meter cd/m 2 mass fraction kilogram per kilogram, which may be represented by the number 1
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SI_units_NIST - Essentials of the SI Base derived units...

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