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The pound or pound-mass is a unit of mass used in both the British imperial and United States customary systems of measurement. Various definitions have been used; the most common today is the international avoirdupois pound, which is legally defined as exactly 0.453 592 37 kilograms, and which is divided into 16 avoirdupois ounces. [ 1]
The kilogram (kg) is the unit of mass. The ampere (A) is the unit of electric current. The kelvin (K) is the unit of thermodynamic temperature. The mole (mol) is the unit of amount of substance. The candela (cd) is the unit of luminous intensity. The SI also defines 22 derived units and associated symbols:
The International System of Units, internationally known by the abbreviation SI (from French Système international d'unités ), is the modern form of the metric system and the world's most widely used system of measurement. Coordinated by the International Bureau of Weights and Measures (abbreviated BIPM from French: Bureau international des ...
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 ΔνCs. — CGPM [ 6][ 7]
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 commerce. Instances in use include the International System of ...
The mass of an object is a measure of the object’s inertial property, or the amount of matter it contains. The weight of an object is a measure of the force exerted on the object by gravity, or the force needed to support it. The pull of gravity on the earth gives an object a downward acceleration of about 9.8 m/s 2.
The tonne (t) is an SI-compatible unit of mass equal to a megagram ( Mg ), or 10 3 kg. The unit is in common use for masses above about 10 3 kg and is often used with SI prefixes. For example, a gigagram ( Gg) or 10 9 g is 10 3 tonnes, commonly called a kilotonne .
Length. For measuring length, the U.S. customary system uses the inch, foot, yard, and mile, which are the only four customary length measurements in everyday use. From 1893, the foot was legally defined as exactly 1200⁄3937 m (approximately 0.304 8006 m ). [ 13] Since July 1, 1959, the units of length have been defined on the basis of 1 yd ...