Weight
- Weight is the title of the 1994 album by the group Rollins Band.
Weight is the
force exerted upon an object by virtue of its position in a
gravitational field. In a constant gravitational field, such as the Earth's, this force is proportional to the object's
mass. Hence, quantitatively, it is given by product of the
mass of the object by the
acceleration due to gravity;
W = m × g. The
SI unit is the
newton (N) or
kilogram metres per second squared (kg · m · s
−2).
The terms
mass and
weight are often used interchangeably and indeed went historically undistinguished. The
CPGM recommends that the word 'weight' be used to refer only to force, and not to mass. The verb 'to weigh' may still be used for mass determinations, although 'to mass' or 'to measure the mass' is also used.
Related to the historical identification of mass and weight, the
pound has been used both as a unit of mass and as a unit of force. In the
United States,
United Kingdom, and elsewhere, the pound is now officially defined as a unit of mass. The corresponding force is called a
pound-force, and similarly the weight of a kilogram of material on Earth is called a
kilogram-force. However, the use of pounds to measure forces is still common in engineering, and it occurs in derived units like
p.s.i (
pounds per square
inch). In most countries, scientists have adopted
SI units, which use
kilogram for mass and
newton for force non-interchangeably.
The weight force that we sense is actually the normal reaction force, which prevents us from being pulled to the centre of the Earth. In contrast, in free-fall, there is no apparent weight because we are not in contact with any surface to provide such a reaction force. The experience of having no weight is known as
weightlessness or microgravity.
Comparative weights on bodies of the solar system
The following is a list of the weights of a mass on some of the bodies in the solar system, relative to its weight on Earth:
{|\n| Mercury || || 0.376\n|-\n| Venus || || 0.903\n|-\n|Earth || = || 1\n|-\n| Moon || || 0.165\n|-\n| Mars || || 0.38\n|-\n| Jupiter || || 2.34\n|-\n| Saturn || || 1.16\n|-\n| Uranus || || 1.15\n|-\n| Neptune || || 1.19\n|-\n| Pluto || || 0.066\n|}
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