{{Short description|Spatial distribution of mass within a solid body}} {{Other uses|Weight distribution}} In physics and mechanics, '''mass distribution''' is the spatial distribution of mass within a solid body. In principle, it is relevant also for gases or liquids, but on Earth their mass distribution is almost homogeneous.
==Astronomy== In astronomy mass distribution has decisive influence on the development e.g. of nebulae, stars and planets. The mass distribution of a '''solid''' defines its center of gravity and influences its dynamical behaviour - e.g. the oscillations and eventual rotation.
==Mathematical modelling== A mass distribution can be modeled as a measure. This allows point masses, line masses, surface masses, as well as masses given by a volume density function. Alternatively the latter can be generalized to a distribution. For example, a point mass is represented by a delta function defined in 3-dimensional space. A surface mass on a surface given by the equation {{math|1=''f'' (''x'', ''y'', ''z'') = 0}} may be represented by a density distribution {{math|1=''g''(''x'', ''y'', ''z'') ''δ''(''f'' (''x'', ''y'', ''z''))}}, where <math display="inline">g/\left|\nabla f\right|</math> is the mass per unit area.
The mathematical modelling can be done by potential theory, by numerical methods (e.g. a great number of mass points), or by theoretical equilibrium figures.
==Geology== In geology the aspects of rock density are involved.
==Rotating solids== Rotating solids are affected considerably by the mass distribution, either if they are homogeneous or inhomogeneous - see Torque, moment of inertia, wobble, imbalance and stability.
==See also== * Bouguer plate * Gravity * Mass function * Mass concentration (astronomy)
==External links== * [https://web.archive.org/web/20070611063816/http://www.geod.uni-bonn.de/apmg/projekte/dfg/schwerpunkt_texte/mass_transport_proposal_spp.pdf Mass distribution of the Earth]
Category:Mechanics Category:Celestial mechanics Category:Geophysics Category:Mass
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