Статика флуида — разлика између измена

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== Притисак у флуидима при мировању ==
 
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Због фундаменталне природе флуида, флуид не може остати у мировању у присуству [[shear stress|смицања]]. Међутим, флуиди могу да врше [[притисак]] [[surface normal|нормално]] на контактну површину. Ако се тачка у флуиду сматра бесконачно малом коцком, онда из принципа равнотеже следи да притисак на свакој страни те јединице мора бити једнак. Да то није био случај, течност би се кретала у правцу резултирајуће силе. Стога, [[fluid pressure|притисак]] на флуид у мировању је [[isotropic|изотропан]]; i.e., он делује са једнаком магнитудом у свим правцима. Ова карактеристика омогућава флуидима да преносе силу кроз дужину цеви; i.e., сила примењена на флуид у цеви се преноси, преко флуида, до другог краја цеви. Овај принцип је првобитно формулисао, у нешто ширем облику [[Блез Паскал]], и стога се назива [[Паскалов закон]].<ref>{{cite web|url=http://www.britannica.com/EBchecked/topic/445445/Pascals-principle|title=Pascal’s principle - Definition, Example, & Facts|author=|date=|website=britannica.com|accessdate=9 May 2018|deadurl=no|archiveurl=https://web.archive.org/web/20150602231705/http://www.britannica.com/EBchecked/topic/445445/Pascals-principle|archivedate=2 June 2015|df=}}</ref><ref>{{cite web|url=https://www.grc.nasa.gov/www/k-12/WindTunnel/Activities/Pascals_principle.html|title=Pascal's Principle and Hydraulics|author=|date=|website=www.grc.nasa.gov|accessdate=9 May 2018|deadurl=no|archiveurl=https://web.archive.org/web/20180405051915/https://www.grc.nasa.gov/www/k-12/WindTunnel/Activities/Pascals_principle.html|archivedate=5 April 2018|df=}}</ref><ref>{{cite web|url=http://hyperphysics.phy-astr.gsu.edu/hbase/pasc.html|title=Pressure|author=|date=|website=hyperphysics.phy-astr.gsu.edu|accessdate=9 May 2018|deadurl=no|archiveurl=https://web.archive.org/web/20171028014050/http://hyperphysics.phy-astr.gsu.edu/hbase/pasc.html|archivedate=28 October 2017|df=}}</ref>
Due to the fundamental nature of fluids, a fluid cannot remain at rest under the presence of a [[shear stress]]. However, fluids can exert [[pressure]] [[surface normal|normal]] to any contacting surface. If a point in the fluid is thought of as an infinitesimally small cube, then it follows from the principles of equilibrium that the pressure on every side of this unit of fluid must be equal. If this were not the case, the fluid would move in the direction of the resulting force. Thus, the [[fluid pressure|pressure]] on a fluid at rest is [[isotropic]]; i.e., it acts with equal magnitude in all directions. This characteristic allows fluids to transmit force through the length of pipes or tubes; i.e., a force applied to a fluid in a pipe is transmitted, via the fluid, to the other end of the pipe. This principle was first formulated, in a slightly extended form, by Blaise Pascal, and is now called [[Pascal's law]].
 
=== Хидростатички притисак ===
{{See also|Вертикалне варијације притиска}}
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InУ aфлуиду fluidу at restмировању, all frictional and inertial stresses vanish and the state of stress of the system is called ''hydrostatic''. When this condition of {{math|''V'' {{=}} 0}} is applied to the [[Navier–Stokes equations|Navier-Stokes equation]], the gradient of pressure becomes a function of body forces only. For a [[barotropic fluid]] in a conservative force field like a gravitational force field, pressure exerted by a fluid at equilibrium becomes a function of force exerted by gravity.
 
The hydrostatic pressure can be determined from a control volume analysis of an infinitesimally small cube of fluid. Since [[pressure]] is defined as the force exerted on a test area ({{math|''p'' {{=}} {{sfrac|''F''|''A''}}}}, with {{mvar|p}}: pressure, {{mvar|F}}: force normal to area {{mvar|A}}, {{mvar|A}}: area), and the only force acting on any such small cube of fluid is the weight of the fluid column above it, hydrostatic pressure can be calculated according to the following formula: