This page is about the physical concept. In law, commerce, and in colloquial usage weight may also refer to mass. For other uses see Weight (disambiguation).
Weight
A diagram explaining the mass and weight
Common symbols
SI unit
newton (N)
Other units
pound-force (lbf)
In SI base units
kg⋅m⋅s−2
Extensive?
Yes
Intensive?
No
Conserved?
No
Derivations from other quantities
Dimension
In science and engineering, the weight of an object, is the force acting on the object due to acceleration or gravity.[1][2][3]
Some standard textbooks[4] define weight as a vector quantity, the gravitational force acting on the object. Others[5][6] define weight as a scalar quantity, the magnitude of the gravitational force. Yet others[7] define it as the magnitude of the reaction force exerted on a body by mechanisms that counteract the effects of gravity: the weight is the quantity that is measured by, for example, a spring scale. Thus, in a state of free fall, the weight would be zero. In this sense of weight, terrestrial objects can be weightless: so if one ignores air resistance, one could say the legendary apple falling from the tree[citation needed], on its way to meet the ground near Isaac Newton, was weightless.
The unit of measurement for weight is that of force, which in the International System of Units (SI) is the newton. For example, an object with a mass of one kilogram has a weight of about 9.8 newtons on the surface of the Earth, and about one-sixth as much on the Moon. Although weight and mass are scientifically distinct quantities, the terms are often confused with each other in everyday use (e.g. comparing and converting force weight in pounds to mass in kilograms and vice versa).[8]
Further complications in elucidating the various concepts of weight have to do with the theory of relativity according to which gravity is modeled as a consequence of the curvature of spacetime. In the teaching community, a considerable debate has existed for over half a century on how to define weight for their students. The current situation is that a multiple set of concepts co-exist and find use in their various contexts.[2]
^Richard C. Morrison (1999). "Weight and gravity - the need for consistent definitions". The Physics Teacher. 37 (1): 51. Bibcode:1999PhTea..37...51M. doi:10.1119/1.880152.
^ abIgal Galili (2001). "Weight versus gravitational force: historical and educational perspectives". International Journal of Science Education. 23 (10): 1073. Bibcode:2001IJSEd..23.1073G. doi:10.1080/09500690110038585. S2CID 11110675.
^Gat, Uri (1988). "The weight of mass and the mess of weight". In Richard Alan Strehlow (ed.). Standardization of Technical Terminology: Principles and Practice – second volume. ASTM International. pp. 45–48. ISBN 978-0-8031-1183-7.
^Knight, Randall D. (2004). Physics for Scientists and Engineers: a Strategic Approach. San Francisco, US: Addison–Wesley. pp. 100–101. ISBN 0-8053-8960-1.
^Bauer, Wolfgang; Westfall, Gary D. (2011). University Physics with Modern Physics. New York: McGraw Hill. p. 103. ISBN 978-0-07-336794-1.
^Serway, Raymond A.; Jewett, John W. (2008). Physics for Scientists and Engineers with Modern Physics. US: Thompson. p. 106. ISBN 978-0-495-11245-7.
^Hewitt, Paul G. (2001). Conceptual Physics. US: Addison–Wesley. pp. 159. ISBN 0-321-05202-1.
^The National Standard of Canada, CAN/CSA-Z234.1-89 Canadian Metric Practice Guide, January 1989:
5.7.3 Considerable confusion exists in the use of the term "weight". In commercial and everyday use, the term "weight" nearly always means mass. In science and technology "weight" has primarily meant a force due to gravity. In scientific and technical work, the term "weight" should be replaced by the term "mass" or "force", depending on the application.
5.7.4 The use of the verb "to weigh" meaning "to determine the mass of", e.g., "I weighed this object and determined its mass to be 5kg," is correct.
engineering, the weight of an object, is the force acting on the object due to acceleration or gravity. Some standard textbooks define weight as a vector quantity...
"The Weight" is a song by the Canadian-American group the Band that was released as a single in 1968 and on the group's debut album Music from Big Pink...
Weight classes are divisions of competition used to match competitors against others of their own size. Weight classes are used in a variety of sports...
Vehicle weight is a measurement of wheeled motor vehicles; either an actual measured weight of the vehicle under defined conditions or a gross weight rating...
Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat (adipose...
Weight Watchers or WW may refer to: Weight Watchers (diet), a comprehensive weight loss program and diet WW International, the company producing the Weight...
a weight class in combat sports and rowing. The lightweight division is over 130 pounds (59 kilograms) and up to 135 pounds (61.2 kilograms) weight class...
Weight for Age (WFA) is a term in thoroughbred horse racing which is one of the conditions for a race. The principle of WFA was developed by Admiral Rous...
Troy weight is a system of units of mass that originated in 15th-century Kingdom of England and is primarily used in the precious metals industry. The...
Human body weight is a person's mass or weight. Strictly speaking, body weight is the measurement of weight without items located on the person. Practically...
Tare weight /ˈtɛər/, sometimes called unladen weight, is the weight of an empty vehicle or container. By subtracting tare weight from gross weight (laden...
Weight gain is an increase in body weight. This can involve an increase in muscle mass, fat deposits, excess fluids such as water or other factors. Weight...
International, Inc., formerly Weight Watchers International, Inc., is a global company headquartered in the U.S. that offers weight loss and maintenance, fitness...
Weight distribution is the apportioning of weight within a vehicle, especially cars, airplanes, and trains. Typically, it is written in the form x/y,...
Jupiter is the fifth planet from the Sun and the largest in the Solar System. A gas giant, Jupiter's mass is more than two and a half times that of all...
Vocal weight refers to the perceived "lightness" or "heaviness" of a singing voice. This quality of the voice is one of the major determining factors in...
The specific weight, also known as the unit weight (symbol γ, the Greek letter gamma), is a volume-specific quantity defined as the weight per unit volume...
Birth weight is the body weight of a baby at their birth. The average birth weight in babies of European and African descent is 3.5 kilograms (7.7 lb)...
maximum takeoff weight (MTOW) or maximum gross takeoff weight (MGTOW) or maximum takeoff mass (MTOM) of an aircraft is the maximum weight at which the pilot...
"Carry That Weight" is a song by the English rock band the Beatles from their 1969 album Abbey Road. Written by Paul McCartney and credited to Lennon–McCartney...
In chemistry, the molar mass (or molecular weight) (M) of a chemical compound is defined as the ratio between the mass and the amount of substance (measured...
Two sports have events that fall under the name of weight throw (Scottish Gaelic: caitheamh cuideam) one being the track and field event and the other...
In chemistry, equivalent weight (also known as gram equivalent or equivalent mass) is the mass of one equivalent, that is the mass of a given substance...
weight class. In international competition, men's freestyle wrestling, men's Greco-Roman wrestling, and female wrestling utilize the following weight...
A weight function is a mathematical device used when performing a sum, integral, or average to give some elements more "weight" or influence on the result...
activity. Moreover, weight management involves developing meaningful ways to track weight over time and to identify the ideal body weights for different individuals...
Yarn weight refers to the thickness of yarn used by knitters, weavers, crocheters and other fiber artists. Changing yarn weight or needle size can have...