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Conversions between units in the metric system are defined by their prefixes (for example, 1 kilogram = 1000 grams, 1 milligram = 0.001 grams) and are thus not listed in this article. Exceptions are made if the unit is commonly known by another name (for example, 1 micron = 10 −6 metre).
The solar flux unit is a unit of spectral irradiance equal to 10 −22 W⋅m −2 ⋅Hz −1 (100 yW⋅m −2 ⋅Hz −1). The nox (nx) is a unit of illuminance equal to 1 millilux (1 mlx). The nit (nt) is a unit of luminance equal to one candela per metre squared (1 cd⋅m −2). The lambert (L) is a unit of luminance equal to 10 4 /π cd⋅m ...
The unit was born out of the necessity to measure land surface to calculate taxes. At the time of Toyotomi Hideyoshi (16th century), the ken was about 1.97 m (6.5 ft), but around 1650 the Tokugawa shogunate reduced it to 1.818 m (5.96 ft) specifically to increase taxes. After the Edo period, the ken started to be called kyōma (京間). [1] [2]
A board foot is a United States and Canadian unit of approximate volume, used for lumber. It is equivalent to 1 inch × 1 foot × 1 foot (144 cu in or 2,360 cm 3). It is also found in the unit of density pounds per board foot. In Australia and New Zealand the terms super foot or superficial foot were formerly used for this unit. The exact ...
Because of the identity property of multiplication, multiplying any quantity (physical or not) by the dimensionless 1 does not change that quantity. [5] Once this and the conversion factor for seconds per hour have been multiplied by the original fraction to cancel out the units mile and hour, 10 miles per hour converts to 4.4704 metres per second.
The rod, perch, or pole (sometimes also lug) is a surveyor's tool [1] and unit of length of various historical definitions. In British imperial and US customary units, it is defined as 16 + 1 ⁄ 2 feet, equal to exactly 1 ⁄ 320 of a mile, or 5 + 1 ⁄ 2 yards (a quarter of a surveyor's chain), and is exactly 5.0292 meters.
The SI has special names for 22 of these coherent derived units (for example, hertz, the SI unit of measurement of frequency), but the rest merely reflect their derivation: for example, the square metre (m 2), the SI derived unit of area; and the kilogram per cubic metre (kg/m 3 or kg⋅m −3), the SI derived unit of density.
Some units have special names, however these should be treated like their equivalents. For example, one newton (N) is equivalent to 1 kg⋅m/s 2. Thus a quantity may have several unit designations, for example: the unit for surface tension can be referred to as either N/m (newton per metre) or kg/s 2 (kilogram per second squared).