Editing Mechanics (section)

== Types of mechanical bodies ==
The often-used term '''[[Physical body|body]]''' needs to stand for a wide assortment of objects, including [[Particle|particles]], [[projectiles]], [[spacecraft]], [[star]]s, parts of [[mechanical engineering|machinery]], parts of [[solids]], parts of [[fluids]] ([[gases]] and [[liquids]]), etc.

Other distinctions between the various sub-disciplines of mechanics concern the nature of the bodies being described. Particles are bodies with little (known) internal structure, treated as mathematical points in classical mechanics. Rigid bodies have size and shape, but retain a simplicity close to that of the particle, adding just a few so-called [[degrees of freedom (physics and chemistry)|degrees of freedom]], such as orientation in space.

Otherwise, bodies may be semi-rigid, i.e. [[Elasticity (physics)|elastic]], or non-rigid, i.e. [[fluid]]. These subjects have both classical and quantum divisions of study.

For instance, the motion of a spacecraft, regarding its [[orbit]] and attitude ([[rotation]]), is described by the relativistic theory of classical mechanics, while the analogous movements of an [[atomic nucleus]] are described by quantum mechanics.