Editing Inelastic collision (section)

{{Short description|Collision in which energy is lost to heat}}
{{More citations needed|date=February 2023}}
[[Image:Bouncing ball strobe edit.jpg|thumb|right|350px|A [[bouncing ball]] captured with a stroboscopic flash at 25 images per second. Each impact of the ball is inelastic, meaning that energy dissipates at each bounce. Ignoring [[air resistance]], the square root of the ratio of the height of one bounce to that of the preceding bounce gives the [[coefficient of restitution]] for the ball/surface impact.]]
An '''inelastic collision''', in contrast to an [[elastic collision]], is a [[collision]] in which kinetic energy is not conserved due to the action of [[Friction#Internal friction|internal friction]].

In collisions of macroscopic bodies, some [[kinetic energy]] is turned into vibrational energy of the [[atom]]s, causing a [[heat]]ing effect, and the bodies are deformed.

The [[molecule]]s of a [[gas]] or [[liquid]] rarely experience perfectly [[elastic collision]]s because kinetic energy is exchanged between the molecules' translational motion and their internal [[Degrees of freedom (physics and chemistry)|degrees of freedom]] with each collision. At any one instant, half the collisions are &ndash; to a varying extent &ndash; inelastic (the pair possesses less kinetic energy after the collision than before), and half could be described as “super-elastic” (possessing ''more'' kinetic energy after the collision than before). Averaged across an entire sample, molecular collisions are elastic. <ref>{{Cite journal |last=Hernandez |first=Hugo |date=2023 |title=Confusion and Illusions in Collision Theory |url=https://rgdoi.net/10.13140/RG.2.2.24913.10088 |journal=ForsChem Research Reports |language=en |volume=8 |doi=10.13140/RG.2.2.24913.10088 |access-date=25 August 2024 |via=ResearchGate}}</ref>

Although inelastic collisions do not conserve kinetic energy, they do obey [[conservation of momentum]].<ref>{{cite book| title = Vector equations for engineers: Dynamics | author = Ferdinand Beer Jr. and E. Russell Johnston | edition = Sixth | publisher = McGraw Hill | year = 1996 | pages = 794–797 | isbn = 978-0070053663 | quote = If the sum of the external forces is zero ... ''the total momentum of the particles is conserved''. ''In the general case of impact'', i.e., when ''e'' is not equal to 1, ''the total energy of the particles is not conserved''.}}</ref> Simple [[ballistic pendulum]] problems obey the conservation of kinetic energy ''only'' when the block swings to its largest angle.

In [[nuclear physics]], an inelastic collision is one in which the incoming [[subatomic particle|particle]] causes the [[atomic nucleus|nucleus]] it strikes to become [[excited state|excited]] or to break up. [[Deep inelastic scattering]] is a method of probing the structure of subatomic particles in much the same way as Rutherford probed the inside of the atom (see [[Rutherford scattering]]). Such experiments were performed on [[proton]]s in the late 1960s using high-energy [[electron]]s at the [[Stanford Linear Accelerator]] (SLAC). As in Rutherford scattering, deep inelastic scattering of electrons by proton targets revealed that most of the incident electrons interact very little and pass straight through, with only a small number bouncing back. This indicates that the charge in the proton is concentrated in small lumps, reminiscent of Rutherford's discovery that the [[electric charge|positive charge]] in an atom is concentrated at the nucleus. However, in the case of the proton, the evidence suggested three distinct concentrations of charge ([[quark]]s) and not one.