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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 = 0.9144 ...
The inch (symbol: in or ″) is a unit of length in the British Imperial and the United States customary systems of measurement. It is equal to 1 / 36 yard or 1 / 12 of a foot . Derived from the Roman uncia ("twelfth"), the word inch is also sometimes used to translate similar units in other measurement systems, usually ...
A variety of units of measurement were used in the various independent Italian states and Italian dependencies of foreign empires up to the unification of Italy in the 19th century. The units to measure length, volume, mass, etc., could differ widely between countries or between towns in a country (e.g. Rome and Ancona), but usually not between ...
Imperial units differing from the above (as the Imperial gallon and bushel differ from the US units) in practice are rarely used, though found in older documents. The Imperial gallon was based on the concept that an Imperial fluid ounce of water would have a mass of one Avoirdupois ounce, and indeed 1 g/cm 3 ≈ 1.00224129 ounces per Imperial ...
Planck units modified so that 8 π G = 1 are known as reduced Planck units, because the Planck mass is divided by √ 8 π. Also, the Bekenstein–Hawking formula for the entropy of a black hole simplifies to S BH = ( m BH ) 2 /2 = 2 π A BH .
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,265 astronomical units (AU), i.e. 30.9 trillion kilometres (19.2 trillion miles).
The Richter scale [1] (/ ˈ r ɪ k t ər /), also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale, [2] is a measure of the strength of earthquakes, developed by Charles Richter in collaboration with Beno Gutenberg, and presented in Richter's landmark 1935 paper, where he called it the "magnitude scale". [3]
Citing measurements made at the 1926 Iowa State Fair, they reported that the peak power over a few seconds has been measured to be as high as 14.88 hp (11.10 kW) [12] and also observed that for sustained activity, a work rate of about 1 hp (0.75 kW) per horse is consistent with agricultural advice from both the 19th and 20th centuries and also ...