Weight
- Weight is the title of the 1994 album by the group Rollins Band.
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.
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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:
Comparative weights on bodies of the solar system
| Mercury | 0.376 | |
| Venus | 0.903 | |
| Earth | = | 1 |
| Moon | 0.165 | |
| Mars | 0.38 | |
| Jupiter | 2.34 | |
| Saturn | 1.16 | |
| Uranus | 1.15 | |
| Neptune | 1.19 | |
| Pluto | 0.066 |