Pub. date: 2010 | Online Pub. Date: December 16, 2009 | DOI: 10.4135/9781412972000 | Print ISBN: 9781412940818 | Online ISBN: 9781412972000| Publisher:SAGE Publications, Inc.About this encyclopedia
Helen E. Ross
In popular language, weight can mean an object (such as a paperweight), the weight of that object, or the mass of that object. In physics, a distinction is made between weight and mass . Weight is a force, usually the result of Earth's gravity acting on an object; weight is defined as mass times acceleration, so weight varies under different gravitational or accelerative forces. Mass is the amount of matter in an object, and it can be measured by the ratio of an applied force to the resulting acceleration; it remains constant under different forces. On Earth, weight information is normally available through the pressure sense because of the constant acceleration of gravity. Inertial mass information is also available if observers move the object and note the force they have applied and the resulting acceleration. Under weightless conditions, as in orbital space travel, only mass information is available. In this ...