Search results
Results from the WOW.Com Content Network
A unit of measurement, or unit of measure, is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. [1] Any other quantity of that kind can be expressed as a multiple of the unit of measurement. [2] For example, a length is a physical quantity.
A system of units of measurement, also known as a system of units or system of measurement, is a collection of units of measurement and rules relating them to each other. . Systems of measurement have historically been important, regulated and defined for the purposes of science and comme
The SI units are defined by declaring that seven defining constants [1]: 125–129 have certain exact numerical values when expressed in terms of their SI units. The realisation of the definition of a unit is the procedure by which the definition may be used to establish the value and associated uncertainty of a quantity of the same kind as the ...
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 einstein (E) has two conflicting definitions. The original is a unit of energy, equal to the energy in one mole (1 mol) of photons. The second is a unit of amount of photons, equal to one mole (1 mol) of photons. The rayleigh (R) is a unit of photon flux rate density equal to 10 10 m −2 ⋅s −1 (10 4 mm −2 ⋅s −1).
The TU (for time unit) is a unit of time defined as 1024 μs for use in engineering. The svedberg is a time unit used for sedimentation rates (usually of proteins). It is defined as 10 −13 seconds (100 fs). The galactic year, based on the rotation of the galaxy and usually measured in million years. [2]
United States customary units form a system of measurement units commonly used in the United States and most U.S. territories [1] since being standardized and adopted in 1832. [2] The United States customary system developed from English units that were in use in the British Empire before the U.S. became an independent country.
The basic unit of length in the imperial and U.S. customary systems is the yard, defined as exactly 0.9144 m by international treaty in 1959. [2] [5] Common imperial units and U.S. customary units of length include: [6] thou or mil (1 ⁄ 1000 of an inch) inch (25.4 mm) foot (12 inches, 0.3048 m) yard (3 feet, 0.9144 m)