page_title: Mass versus weight
section_title: Converting units of mass to equivalent forces on Earth
hierarchical_section_title: Mass versus weight / Converting units of mass to equivalent forces on Earth
caption_attribution_description: English: Gravity map of the Southern Ocean around the Antarctic continent This gravity field was computed from sea-surface height measurements collected by the US Navy GEOSAT altimeter between March, 1985, and January, 1990. The high density GEOSAT Geodetic Mission data that lie south of 30 deg. S were declassified by the Navy in May of 1992 and contribute most of the fine-scale gravity information. The Antarctic continent itself is shaded in blue depending on the thickness of the ice sheet (blue shades in steps of 1000 m); light blue is shelf ice; gray lines are the major ice devides; pink spots are parts of the continent which are not covered by ice; gray areas have no data. Français&#160;: Carte gravimétrique de l'océan Austral et du continent antarctique Ce champ de gravité a été calculé à partir de mesures de hauteur des eaux de surface recueillies par l'altimètre de l'US Navy GEOSAT de Mars 1985 à Janvier 1990. Les données récolées par la mission "high density GEOSAT Geodetic Mission data" ont été déclassifiées par la Marine, en mai 1992 et fournissent la plupart des informations sur la gravité à petite échelle. Le continent antarctique lui-même est coloré en bleu selon l'épaisseur de la calotte glaciaire (Chaque nuances de bleu correspond à une étape de 1000 m)&#160;; lignes grises matérialisent les bassins versants de glace; les taches roses sont les parties du continent qui ne sont pas couvertes par la glace, les zones grises sont celles pour lesquelles on manque de données
context_page_description: In common usage, the mass of an object is often referred to as its weight, though these are in fact different concepts and quantities. In scientific contexts, mass is the amount of "matter" in an object, whereas weight is the force exerted on an object by gravity. In other words, an object with a mass of 1.0 kilogram weighs approximately 9.81 newtons on the surface of the Earth, which is its mass multiplied by the gravitational field strength. The object's weight is less on Mars, where gravity is weaker, and more on Saturn, and very small in space when far from any significant source of gravity, but it always has the same mass.
  Objects on the surface of the Earth have weight, although sometimes the weight is difficult to measure. An example is a small object floating in water, which does not appear to have weight since it is buoyed by the water; but it is found to have its usual weight when it is added to water in a container which is entirely supported by and weighed on a scale. Thus, the "weightless object" floating in water actually transfers its weight to the bottom of the container.
context_section_description: When an object's weight (its gravitational force) is expressed in "kilograms", this actually refers to the kilogram-force (kgf or kg-f), also known as the kilopond (kp), which is a non-SI unit of force. All objects on the Earth's surface are subject to a gravitational acceleration of approximately 9.8 m/s². The General Conference on Weights and Measures fixed the value of standard gravity at precisely 9.80665 m/s² so that disciplines such as metrology would have a standard value for converting units of defined mass into defined forces and pressures. Thus the kilogram-force is defined as precisely 9.80665 newtons. In reality, gravitational acceleration (symbol: g) varies slightly with latitude, elevation and subsurface density; these variations are typically only a few tenths of a percent. See also Gravimetry.
  Engineers and scientists understand the distinctions between mass, force, and weight. Engineers in disciplines involving weight loading (force on a structure due to gravity), such as structural engineering, convert the mass of objects like concrete and automobiles (expressed in kilograms) to a force in newtons (by multiplying by some factor around 9.8; 2 significant figures is usually sufficient for such calculations) to derive the load of the object. Material properties like elastic modulus are measured and published in terms of the newton and pascal (a unit of pressure related to the newton).
caption: Gravity anomalies covering the Southern Ocean are shown here in false-color relief. This image has been normalized to remove variation due to differences in latitude.
exif: {}