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From Nordan Symposia
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==Etymology==
[http://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] wight, weght, from [http://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] wiht; akin to Old Norse vætt weight, Old English wegan to weigh
*Date: before [http://www.wikipedia.org/wiki/11th_Century 12th century]
==Definitions==
*1 a : the amount that a [[thing]] weighs b (1) : the [[standard]] or established amount that a thing should weigh (2) : one of the classes into which contestants in a [[sports]] event are divided according to [[body]] weight (3) : poundage required to be carried by a horse in a handicap race
*2 a : a [[quantity]] or thing weighing a fixed and usually specified amount
:b : a heavy object (as a metal ball) thrown, put, or lifted as an [[athletic]] [[exercise]] or contest
*3 a : a [[unit]] of weight or [[mass]] — see metric system table
:b : a piece of [[material]] (as metal) of known specified weight for use in weighing articles
:c : a system of related units of weight
*4 a : something heavy : load
:b : a heavy object to hold or press something down or to counterbalance
*5 a : burden, pressure <the weight of their responsibilities>
:b : the [[quality]] or [[state]] of [[being]] ponderous
:c : corpulence
*6 a : [[relative]] heaviness : mass
:b : the [[force]] with which a [[body]] is attracted toward the [[earth]] or a [[celestial]] body by gravitation and which is equal to the product of the mass and the local gravitational acceleration
*7 a : the [[relative]] importance or [[authority]] accorded something <the weight of her [[opinion]]s>
:b : measurable [[influence]] especially on others <throwing his weight behind the proposal>
*8 : overpowering [[force]]
*9 : the [[quality]] (as lightness) that makes a fabric or garment suitable for a particular use or season —often used in combination <summer-weight>
*10 : a numerical coefficient assigned to an item to [[express]] its [[relative]] importance in a [[frequency]] [[distribution]]
*11 : the [[degree]] of thickness of the strokes of a type character
==Description==
In the [[Natural Sciences|physical sciences]], the '''weight''' of an object is the [[magnitude]], W, of the [[force]] that must be applied to an object in order to support it (i.e. hold it at rest) in a [[gravitational]] field. The weight of an object in [[static]] [[equilibrium]] equals the magnitude of the gravitational force acting on the object, less the [[effect]] of its [[buoyancy]] in any fluid in which it might be immersed.[1] Near the [[surface]] of the [[Earth]], the acceleration due to [[gravity]] is approximately constant; this means that an object's weight near the surface of the Earth is roughly [[proportional]] to its [[mass]].
In [[practical]] or everyday [[application]]s, weight means the same as mass as that term is used in [[physics]]. In modern [[scientific]] usage, however, '''weight''' and '''mass''' are fundamentally [[different]] quantities: mass is an [[intrinsic]] property of [[matter]], whereas weight is a [[force]] that results from the action of [[gravity]] on matter: it measures how strongly gravity pulls on that matter.
However, the recognition of this difference is historically a [[relatively]] recent [[development]] and in many everyday situations the word "weight" continues to be used when, strictly, "mass" is meant. For example, most people would say that an object "weighs one kilogram", even though the kilogram is a [[unit]] of mass.
The distinction between mass and weight is unimportant for many practical [[purposes]] because the strength of [[gravity]] is very similar everywhere on the [[surface]] of the [[Earth]]. In such a constant gravitational field, the gravitational force exerted on an object (its weight) is directly [[proportional]] to its mass. For example, object A weighs 10 times as much as object B, so therefore the mass of object A is 10 times greater than that of object B. This means that an object's mass can be measured indirectly by its weight
Nevertheless, the Earth's gravitational field can vary by as much as 0.5% at different locations on Earth. These variations alter the [[relationship]] between weight and mass, and must be taken into account in high precision weight [[measurements]] that are intended to indirectly measure mass. To eliminate this variation, when the weight of objects is used in [[Business|commerce]], the [[value]] given is what the objects would weigh at a nominal [[standard]] gravitational acceleration of 9.80665 m/s2 (approx. 32.174 ft/s2). Spring scales, which measure local weight, must be calibrated at the location at which the objects will be used to show this standard weight, to be legal for commerce.
The use of "weight" for "mass" also persists in some scientific terminology – for example, the [[chemical]] terms "atomic weight", "molecular weight", and "formula weight", can still be found rather than the preferred "[http://en.wikipedia.org/wiki/Atomic_mass atomic mass]" etc.
The difference between mass and weight is apparent when, for example:
*objects are compared in different gravitational fields, such as away from the Earth's surface. For example, on the surface of the Moon, gravity is only about one-sixth as strong as on the surface of the Earth. A one-kilogram mass is still a one-kilogram mass (as mass is an intrinsic property of the object) but the downward force due to gravity is only one-sixth of what the object would experience on Earth.
*an object is immersed in a liquid or gas. For instance, a brick weighs less when suspended in water, even though its mass is unchanged, and a helium balloon in the atmosphere appears to have negative weight, even though its mass is positive.[http://en.wikipedia.org/wiki/Weight]
[[Category: Physics]]
==Etymology==
[http://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] wight, weght, from [http://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] wiht; akin to Old Norse vætt weight, Old English wegan to weigh
*Date: before [http://www.wikipedia.org/wiki/11th_Century 12th century]
==Definitions==
*1 a : the amount that a [[thing]] weighs b (1) : the [[standard]] or established amount that a thing should weigh (2) : one of the classes into which contestants in a [[sports]] event are divided according to [[body]] weight (3) : poundage required to be carried by a horse in a handicap race
*2 a : a [[quantity]] or thing weighing a fixed and usually specified amount
:b : a heavy object (as a metal ball) thrown, put, or lifted as an [[athletic]] [[exercise]] or contest
*3 a : a [[unit]] of weight or [[mass]] — see metric system table
:b : a piece of [[material]] (as metal) of known specified weight for use in weighing articles
:c : a system of related units of weight
*4 a : something heavy : load
:b : a heavy object to hold or press something down or to counterbalance
*5 a : burden, pressure <the weight of their responsibilities>
:b : the [[quality]] or [[state]] of [[being]] ponderous
:c : corpulence
*6 a : [[relative]] heaviness : mass
:b : the [[force]] with which a [[body]] is attracted toward the [[earth]] or a [[celestial]] body by gravitation and which is equal to the product of the mass and the local gravitational acceleration
*7 a : the [[relative]] importance or [[authority]] accorded something <the weight of her [[opinion]]s>
:b : measurable [[influence]] especially on others <throwing his weight behind the proposal>
*8 : overpowering [[force]]
*9 : the [[quality]] (as lightness) that makes a fabric or garment suitable for a particular use or season —often used in combination <summer-weight>
*10 : a numerical coefficient assigned to an item to [[express]] its [[relative]] importance in a [[frequency]] [[distribution]]
*11 : the [[degree]] of thickness of the strokes of a type character
==Description==
In the [[Natural Sciences|physical sciences]], the '''weight''' of an object is the [[magnitude]], W, of the [[force]] that must be applied to an object in order to support it (i.e. hold it at rest) in a [[gravitational]] field. The weight of an object in [[static]] [[equilibrium]] equals the magnitude of the gravitational force acting on the object, less the [[effect]] of its [[buoyancy]] in any fluid in which it might be immersed.[1] Near the [[surface]] of the [[Earth]], the acceleration due to [[gravity]] is approximately constant; this means that an object's weight near the surface of the Earth is roughly [[proportional]] to its [[mass]].
In [[practical]] or everyday [[application]]s, weight means the same as mass as that term is used in [[physics]]. In modern [[scientific]] usage, however, '''weight''' and '''mass''' are fundamentally [[different]] quantities: mass is an [[intrinsic]] property of [[matter]], whereas weight is a [[force]] that results from the action of [[gravity]] on matter: it measures how strongly gravity pulls on that matter.
However, the recognition of this difference is historically a [[relatively]] recent [[development]] and in many everyday situations the word "weight" continues to be used when, strictly, "mass" is meant. For example, most people would say that an object "weighs one kilogram", even though the kilogram is a [[unit]] of mass.
The distinction between mass and weight is unimportant for many practical [[purposes]] because the strength of [[gravity]] is very similar everywhere on the [[surface]] of the [[Earth]]. In such a constant gravitational field, the gravitational force exerted on an object (its weight) is directly [[proportional]] to its mass. For example, object A weighs 10 times as much as object B, so therefore the mass of object A is 10 times greater than that of object B. This means that an object's mass can be measured indirectly by its weight
Nevertheless, the Earth's gravitational field can vary by as much as 0.5% at different locations on Earth. These variations alter the [[relationship]] between weight and mass, and must be taken into account in high precision weight [[measurements]] that are intended to indirectly measure mass. To eliminate this variation, when the weight of objects is used in [[Business|commerce]], the [[value]] given is what the objects would weigh at a nominal [[standard]] gravitational acceleration of 9.80665 m/s2 (approx. 32.174 ft/s2). Spring scales, which measure local weight, must be calibrated at the location at which the objects will be used to show this standard weight, to be legal for commerce.
The use of "weight" for "mass" also persists in some scientific terminology – for example, the [[chemical]] terms "atomic weight", "molecular weight", and "formula weight", can still be found rather than the preferred "[http://en.wikipedia.org/wiki/Atomic_mass atomic mass]" etc.
The difference between mass and weight is apparent when, for example:
*objects are compared in different gravitational fields, such as away from the Earth's surface. For example, on the surface of the Moon, gravity is only about one-sixth as strong as on the surface of the Earth. A one-kilogram mass is still a one-kilogram mass (as mass is an intrinsic property of the object) but the downward force due to gravity is only one-sixth of what the object would experience on Earth.
*an object is immersed in a liquid or gas. For instance, a brick weighs less when suspended in water, even though its mass is unchanged, and a helium balloon in the atmosphere appears to have negative weight, even though its mass is positive.[http://en.wikipedia.org/wiki/Weight]
[[Category: Physics]]
