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English units of measurement

English units of measurement, principal system of weights and measures used in a few nations, the only major industrial one being the United States. It actually consists of two related systems—the U.S. Customary System of units, used in the United States and dependencies, and the British Imperial System. The names of the units and the relationships between them are generally the same in both systems, but the sizes of the units differ, sometimes considerably.

Customary Units of Weights and Measures

Units of Weight

The pound (lb) is the basic unit of weight (which is proportional to mass). Within the English units of measurement there are three different systems of weights. In the avoirdupois system, the most widely used of the three, the pound is divided into 16 ounces (oz) and the ounce into 16 drams. The ton, used to measure large masses, is equal to 2,000 lb (short ton) or 2,240 lb (long ton). In Great Britain the stone, equal to 14 lb, is also used. The troy system (named for Troyes, France, where it is said to have originated) is used only for precious metals. The troy pound is divided into 12 ounces and the troy ounce into 20 pennyweights or 480 grains; the troy pound is thus 5,760 grains. The grain is also a unit in the avoirdupois system, 1 avoirdupois pound being 7,000 grains, so that the troy pound is 5,760/7,000 of an avoirdupois pound. Apothecaries' weights are based on troy weights; in addition to the pound, ounce, and grain, which are equal to the troy units of the same name, other units are the dram (1/8 oz) and the scruple (1/24 oz or 1/3 dram).

Units of Length and Area

The basic unit of length is the yard (yd); fractions of the yard are the inch (1/36 yd) and the foot (1/3 yd), and commonly used multiples are the rod (51-2 yd), the furlong (220 yd), and the mile (1,760 yd). The acre, equal to 4,840 square yards or 160 square rods, is used for measuring land area.

Units of Liquid Measure

For liquid measure, or liquid capacity, the basic unit is the gallon, which is divided into 4 quarts, 8 pints, or 32 gills. The U.S. gallon, or wine gallon, is 231 cubic inches (cu in.); the British imperial gallon is the volume of 10 lb of pure water at 62℉ and is equal to 277.42 cu in. The British units of liquid capacity are thus about 20% larger than the corresponding American units. The U.S. fluid ounce is 1/16 of a U.S. pint; the British unit of the same name is 1/20 of an imperial pint and is thus slightly smaller than the U.S. fluid ounce.

Units of Dry Measure

For dry measure, or dry capacity, the basic unit is the bushel, which is divided into 4 pecks, 32 dry quarts, or 64 dry pints. The U.S. bushel, or Winchester bushel, is 2,150.42 cu in. and is about 3% smaller than the British imperial bushel of 2,219.36 cu in., with a similar difference existing between U.S. and British subdivisions. The barrel is a unit for measuring the capacity of larger quantities and has various legal definitions depending on the quantity being measured, the most common value being 105 dry quarts.

Differences between American and British Systems

Many American units of weights and measures are based on units in use in Great Britain before 1824, when the British Imperial System was established. Since the Mendenhall Order of 1893, the U.S. yard and pound and all other units derived from them have been defined in terms of the metric units of length and mass, the meter and the kilogram; thus, there was no longer any direct relationship between American units and British units of the same name. In 1959 an international agreement was reached among English-speaking nations to use the same metric equivalents for the yard and pound for purposes of science and technology; these values are 1 yd=0.9144 meter (m) and 1 lb=0.45359237 kilogram (kg). In the United States, the older definition of the yard as 3,600/3,937 m has continued to be used in many instances for surveying, the corresponding foot (1,200/3,937 m) being known as the survey foot; the survey foot will become obsolete in 2023.

The English units of measurement have many drawbacks: the complexity of converting from one unit to another, the differences between American and British units, the use of the same name for different units (e.g., ounce for both weight and liquid capacity, quart and pint for both liquid and dry capacity), and the existence of three different systems of weights (avoirdupois, troy, and apothecaries'). Because of these disadvantages and because of the wide use of the much simpler metric system in most other parts of the world, there have been proposals to do away with the U.S. Customary System and replace it with the metric system.

Bibliography

See L. J. Chisholm, Units of Weights and Measure: International and U.S. Customary (U.S. National Bureau of Standards, 1967).

The Columbia Electronic Encyclopedia™ Copyright © 2022, Columbia University Press. Licensed from Columbia University Press. All rights reserved.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Rod

 

(also rod cell), a photoreceptor of the human and lower vertebrate eye. The rod cells respond to faint light. They and the cone cells are located in the outermost part of the retina. The cells consist of a basal synapse (connected with deeper-lying retinal cells), the nucleus, an internal segment containing ergastoplasm, the myoid (a contractile element of the rod cells), the ellipsoid (a mass of mitochondria), and an external segment made up of disks. A connective fiber with nine pairs of threads typical of cilia and departing from a pair of centrioles unites the internal and external segments. The disks of the outer segment, which are composed partly of visual pigment, are formed by an invagination of the cytoplasmic membrane. At the retinal periphery, there are more rod cells than cone cells. The retinas of nocturnal and crepuscular animals contain only rods.

REFERENCE

Vinnikov, la. A. Tsitologicheskie i molekuliarnye osnovy retseptsii. Leningrad, 1971.

O. G. STROEVA


Rod

 

in the theory of oscillations, an elastic solid body whose length greatly exceeds its transverse dimensions. When a rod is excited, for example, by an impact, free oscillations arise in the rod. The oscillatory displacements of the particles of the rod may be directed either along the rod’s axis—longitudinal oscillations—or perpendicular to the axis—torsional and flexural oscillations. For torsional oscillations, any cross section of the rod is twisted with respect to an adjacent cross section. For flexural oscillations, the points of the axis of the rod are displaced in a transverse direction, and fibers parallel to and lying on various sides of the axis undergo tensile and compressive strains.

Any oscillation of a rod may be represented as the sum of the simplest sinusoidals of the various types of natural oscillations in the rod. The frequencies f of the oscillations depend on the length l of the rod, the density p of the material, the shape and area S of the cross section, the elastic reaction to the given type of deformation, and the conditions of attachment of the rod’s ends. For example, for longitudinal oscillations of a free rod,

where E is Young’s modulus and n is an integer corresponding to the number of the harmonic component. For torsional oscillations of a round free rod,

where G is the shear modulus. In the case of flexural oscillations, the natural frequencies do not form a harmonic series, since the rate of propagation of flexural waves is dependent on frequency. For a rod secured at both ends,

where I is the moment of inertia of the cross section with respect to a neutral axis of the rod and the coefficient αn assumes the values α1 = 4.73, α2 = 7.85,. . . The form of the free oscillations of the rod depends on which of the free oscillations are found in the spectrum; this, in turn, is determined by the method of excitation.

Under the action of a sinusoidal driving force the rod oscillates at the frequency of the force f (forced oscillations). When the frequency of the force coincides with one of the rod’s natural frequencies, the phenomenon of resonance occurs.

The practical importance of oscillations of a rod is varied. Any beam in a structural design may be considered as a rod on whose natural frequencies the strength of the structure depends. Dangerous oscillations arising along a ship’s length because of an engine imbalance may be considered as oscillations of a rod. Rods are used in some musical instruments, such as xylophones. A tuning fork is a curved rod with two free ends.

REFERENCES

Morse, P. Kolebaniia i zvuk. Moscow-Leningrad, 1949. (Translated from English.)
Strutt, J. W. (Lord Rayleigh). Teoriia zvuka, 2nd ed., vol. 1. Moscow, 1955. (Translated from English.)
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

rod

[räd]
(design engineering)
A bar whose end is slotted, tapered, or screwed for the attachment of a drill bit.
A thin, round bar of metal or wood.
(geology)
A rodlike sedimentary particle characterized by a width-length ratio less than 2/3 and a thickness-width ratio more than 2/3. Also known as roller.
(histology)
One of the rod-shaped sensory bodies in the retina which are sensitive to dim light.
(mechanics)
(nucleonics)
A relatively long and slender body of material used in, or in conjunction with, a nuclear reactor; may contain fuel, absorber, or fertile material or other material in which activation or transmutation is desired.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

rod

1. In plastering, a straightedge, usually of wood, for leveling the face of a wall.
2. A solid (metal, wood, or plastic) product that is long in relation to its cross section.

straightedge, rod

1. A rigid, straight piece of wood or metal used to strike off a concrete, mortared, or plastered surface; a screed, 2.
2. A long piece of seasoned, planed wood having straight, parallel edges; used in construction to lay out straight lines and to align framing.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

rod

wand or staff carried as a symbol of office and authority. [Western Culture: Misc.]
Allusions—Cultural, Literary, Biblical, and Historical: A Thematic Dictionary. Copyright 2008 The Gale Group, Inc. All rights reserved.

rod

1. a straight slender shoot, stem, or cane of a woody plant
2. See fishing rod
3. 
a. a unit of length equal to 5½ yards
b. a unit of square measure equal to 30¼ square yards
4. a metal shaft that transmits power in axial reciprocating motion
5. any of the elongated cylindrical cells in the retina of the eye, containing the visual purple (rhodopsin), which are sensitive to dim light but not to colour
6. short for hot rod
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Development of enamel is a complex organized process, where the ameloblasts lay down the enamel rods in an undulating and inter-twining path.
(9,10) The undulating course of ameloblast during amelogenesis results in the formation of a specific pattern by so, the course of enamel rods is not the same throughout the thickness of enamel.
Another potential cause for higher failure in the buccal and palatal surfaces could be the enamel rods direction at those surfaces as in buccal or lingual surface cavity preparation; only the sides of the enamel rods are exposed.