View source for Suction

{{short description|Air pressure differential between two areas}}
{{other uses|Suction convention}}

{{Multiple issues|
{{More citations needed|date=January 2024}}
{{Original research|date=December 2022}}
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[[File:Suction vs Blowing.png|thumb|240x240px|Gasses or liquids that move along a pressure gradient can exert forces on objects. Objects can only be pushed by gases or liquids. The correct terminology used depends on whether they are pushed from a pressurized zone towards ambient pressure (blown out) or from ambient pressure towards a low pressure zone (sucked in). Gases and liquids cannot generate pulling forces on objects<ref>{{Cite web |last=Quora |title=There's No Suction In Space, Because Suction Is An Illusion |url=https://www.forbes.com/sites/quora/2016/11/21/theres-no-suction-in-space-because-suction-is-an-illusion/ |access-date=2024-01-16 |website=Forbes |language=en}}</ref>.]]
'''Suction''' is the day-to-day term for forces experienced by objects that are exposed to the movement of [[gas]]es or [[liquid]]s moving along a [[pressure]] gradient. Contrary to popular belief, however, the forces acting in this case do not originate from the lower pressure side (the vacuum), but from the side of the higher pressure.

When the pressure in one part of a [[physical system]] is reduced relative to another, the [[fluid]] or gas in the higher pressure region will exert a [[force]] relative to the region of lowered pressure, referred to as [[pressure-gradient force]]. If all gas or fluid is removed the result is a perfect vacuum in which the pressure is zero. Hence, no negative pressure forces can be generated. Accordingly, from a physics point of view, the objects are not sucked but pushed.

== Examples ==
Pressure reduction may be [[Static pressure|static]], as in a [[piston]] and cylinder arrangement, or [[Dynamic pressure|dynamic]], as in the case of a [[vacuum cleaner]] when air flow results in a reduced pressure region.

When animals breathe, the [[Thoracic diaphragm|diaphragm]] and muscles around the rib cage cause a change of volume in the lungs. The increased volume of the [[chest cavity]] decreases the pressure inside, creating an imbalance with the ambient air pressure, resulting in suction. Similarly, when a straw is used to suck a liquid into the mouth, the atmospheric pressure pushes the liquid through the straw along the pressure gradient.

A common semantic mistake is made when in case of accidents with spaceships or aircraft in which objects are blown out of the vessel in the case of an [[uncontrolled decompression]] which is often wrongly referred to as objects being sucked out.<ref>{{Cite web |last=Quora |title=There's No Suction In Space, Because Suction Is An Illusion |url=https://www.forbes.com/sites/quora/2016/11/21/theres-no-suction-in-space-because-suction-is-an-illusion/ |access-date=2024-01-14 |website=Forbes |language=en}}</ref><ref>{{Cite web |title=Why doesn't Earth's atmosphere escape into space? |url=https://www.spacecentre.nz/resources/faq/solar-system/earth/atmosphere-escape.html |access-date=2024-01-14 |website=www.spacecentre.nz}}</ref>

== See also ==
{{Wiktionary}}
*[[Pump]]
*[[Vacuum pump]]
*[[Suction (medicine)|Suction devices used in medicine]]
*[[Implosion (mechanical process)|Implosion]]
* [[Suction cup]]
* [[Suction cupping]]

== References ==
{{reflist}}

[[Category:Physical quantities]]
[[Category:Units of pressure]]
[[Category:Vacuum]]


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