Weight

gross weightweighingweighnet weightweighedweighsmass forceweightsweightydistinction between force due to gravity and mass
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Gravity

gravitationgravitationalgravitational force
In science and engineering, the weight of an object is related to the force acting on the object, either due to gravity or to a reaction force that holds it in place. In a uniform 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, and so, for everyday purposes, weighing (using a weighing scale) is an entirely acceptable way of measuring mass. Similarly, a balance measures mass indirectly by comparing the weight of the measured item to that of an object(s) of known mass. Since the measured item and the comparison mass are in virtually the same location, so experiencing the same gravitational field, the effect of varying gravity does not affect the comparison or the resulting measurement. In modern scientific usage, 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 the force of gravity pulls on that matter. The Earth's gravitational field is not uniform but can vary by as much as 0.5% at different locations on Earth (see Earth's gravity). A spring scale or hydraulic or pneumatic scale measures local weight, the local force of gravity on the object (strictly apparent weight force).
On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides.

International System of Units

SISI unitsSI unit
The unit of measurement for weight is that of force, which in the International System of Units (SI) is the newton.

Buoyancy

buoyantbuoyant forcefloat
Archimedes saw weight as a quality opposed to buoyancy, with the conflict between the two determining if an object sinks or floats.
Buoyancy or upthrust, is an upward force exerted by a fluid that opposes the weight of an immersed object.

Mass

inertial massgravitational massweight
Weight became fundamentally separate from mass. In modern scientific usage, 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 the force of gravity pulls on that matter.
In physics, mass is not the same as weight, even though mass is often determined by measuring the object's weight using a spring scale, rather than balance scale comparing it directly with known masses.

Weightlessness

zero gravityzero-gzero-gravity
This can make a considerable difference, depending on the details; for example, an object in free fall exerts little if any force on its support, a situation that is commonly referred to as weightlessness.
Weightlessness is the complete or near-complete absence of the sensation of weight.

Standard gravity

gacceleration due to gravityacceleration of gravity
Sometimes, it is simply taken to have a standard value of 9.80665 m/s 2, which gives the standard weight.
This value was established by the 3rd CGPM (1901, CR 70) and used to define the standard weight of an object as the product of its mass and this nominal acceleration.

Weighing scale

scalesscalebalance
In a uniform 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, and so, for everyday purposes, weighing (using a weighing scale) is an entirely acceptable way of measuring mass. Similarly, a balance measures mass indirectly by comparing the weight of the measured item to that of an object(s) of known mass. Since the measured item and the comparison mass are in virtually the same location, so experiencing the same gravitational field, the effect of varying gravity does not affect the comparison or the resulting measurement. A spring scale or hydraulic or pneumatic scale measures local weight, the local force of gravity on the object (strictly apparent weight force).
A Beam balance (or Beam scale) is a device to measure weight or mass.

Intrinsic and extrinsic properties

intrinsicinnateextrinsic
In modern scientific usage, 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 the force of gravity pulls on that matter.
For example, density is an intrinsic property of any physical object, whereas weight is an extrinsic property that depends on another object.

Levitation

levitatelevitatinghover
The apparent weight may be similarly affected by levitation and mechanical suspension.
Levitation (on Earth or any planetoid) requires an upward force that cancels out the weight of the object, so that the object does not fall (accelerate downward) or rise (accelerate upward).

Gravity of Earth

Earth's gravityggravity
The Earth's gravitational field is not uniform but can vary by as much as 0.5% at different locations on Earth (see Earth's gravity).
The weight of an object on Earth's surface is the downwards force on that object, given by Newton's second law of motion, or.

G-force

gg-forcesGs
It is actually the sensation of g-force, regardless of whether this is due to being stationary in the presence of gravity, or, if the person is in motion, the result of any other forces acting on the body such as in the case of acceleration or deceleration of a lift, or centrifugal forces when turning sharply.
The gravitational force equivalent, or, more commonly, g-force, is a measurement of the type of force per unit mass – typically acceleration – that causes a perception of weight, with a g-force of 1 g equal to the conventional value of gravitational acceleration on Earth, g, of about 9.8 m/s2.

Spring scale

spring balancespring scales
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. 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.
A spring scale cannot measure mass, only weight.

Tare weight

tareemptytare mass
Conversely, net weight refers to the weight of the product alone, discounting the weight of its container or packaging; and tare weight is the weight of the packaging alone.
By subtracting it from the gross weight (laden weight), the weight of the goods carried (the net weight) may be determined.

Pound (force)

lbflb f pound-force
So a man of mass 180 pounds weighs only about 30 pounds-force when visiting the Moon.
In the "engineering" systems (middle column), the weight of the mass unit (pound-mass) on Earth's surface is approximately equal to the force unit (pound-force).

Apparent weight

apparent'' weight forceRelation between g-force and apparent weight
A spring scale or hydraulic or pneumatic scale measures local weight, the local force of gravity on the object (strictly apparent weight force).
The apparent weight of an object will differ from the weight of an object whenever the force of gravity acting on the object is not balanced by an equal but opposite normal force.

Kilogram

kgmgmilligram
Used in this sense, the proper SI unit is the kilogram (kg).

Science

scientificsciencesscientific knowledge
In science and engineering, the weight of an object is related to the force acting on the object, either due to gravity or to a reaction force that holds it in place.

Engineering

engineerengineersengineered
In science and engineering, the weight of an object is related to the force acting on the object, either due to gravity or to a reaction force that holds it in place.

Force

forcesattractiveelastic force
In science and engineering, the weight of an object is related to the force acting on the object, either due to gravity or to a reaction force that holds it in place. The unit of measurement for weight is that of force, which in the International System of Units (SI) is the newton. A spring scale or hydraulic or pneumatic scale measures local weight, the local force of gravity on the object (strictly apparent weight force).

Euclidean vector

vectorvectorsvector addition
Some standard textbooks define weight as a vector quantity, the gravitational force acting on the object.

Free fall

free-fallfreefallfree-falling
This can make a considerable difference, depending on the details; for example, an object in free fall exerts little if any force on its support, a situation that is commonly referred to as weightlessness. Thus, in a state of free fall, the weight would be zero.

Drag (physics)

dragaerodynamic dragair resistance
In this sense of weight, terrestrial objects can be weightless: ignoring air resistance, the famous apple falling from the tree, on its way to meet the ground near Isaac Newton, would be weightless.

Isaac Newton

NewtonSir Isaac NewtonNewtonian
In this sense of weight, terrestrial objects can be weightless: ignoring air resistance, the famous apple falling from the tree, on its way to meet the ground near Isaac Newton, would be weightless.

Unit of measurement

unitunits of measurementweights and measures
The unit of measurement for weight is that of force, which in the International System of Units (SI) is the newton.

Newton (unit)

kNnewtonN
The unit of measurement for weight is that of force, which in the International System of Units (SI) is the newton.