Name: pascal’s principle in static fluids
Uploaded: 2023-04-30T11:04:20.000Z
Duration: 1 min 4 s
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K12 Standards

Alabama Course of Study Science

9-12

Physics

motion-and-stability-forces-and-interactions

Motion and Stability: Forces and Interactions

9-12.P.1.4.b

Pascal's Law

Le principe de Pascal stipule que si la pression dans un fluide confiné est modifiée, le changement est transmis à l'ensemble du fluide et aux parois du récipient sans être diminué en ampleur.
Pour comprendre ce principe, considérons un pistolet à eau à buses multiples de section transversale A rempli d’eau.
Lorsque le piston est pressé avec une force F, le changement de pression correspondant F/A est transmis à travers tout le volume d’eau et atteint chaque buse.
L'eau s'écoule avec la même pression à travers chaque buse, selon le principe de Pascal.
En prenant un autre exemple, qu’un baril soit relié à un long tuyau mince à travers lequel l’eau est versée.
Lorsque le baril est plein et qu’une quantité supplémentaire d’eau y est versée, la pression exercée par l’eau entrante augmente rapidement dans tout son volume dans le tonneau, ce qui la fait fuir de tous les côtés.

la loi de pascal

En 1653, le philosophe et scientifique français Blaise Pascal a publié "Traité de l'équilibre des liquides", qui traitait des principes des fluides statiques. Un fluide statique est un fluide qui ne se déplace pas. Lorsqu'un fluide ne s'écoule pas, on dit que le fluide est en équilibre statique. Si le fluide est de l'eau, on dit qu'il est en équilibre hydrostatique. Pour un fluide en équilibre statique, la force nette sur n'importe quelle partie du fluide doit être nulle; sinon, le fluide commencera à s'écouler. Pascal a observé qu'un changement de pression appliqué à un fluide clos est transmis sans diminution à travers le fluide et aux parois de son contenant. De plus, le principe de Pascal implique que la pression totale dans un fluide est la somme des pressions provenant de différentes sources. Par exemple, la pression à une certaine profondeur dans un fluide dépend de la profondeur du fluide et de la pression de l'atmosphère.

Dans un fluide clos, étant donné que les atomes du fluide sont libres de se déplacer, ils transmettent la pression à toutes les parties du fluide et aux parois du contenant. Tout changement de pression est transmis sans diminution. Notez que ce principe ne dit pas que la pression est la même en tous points d'un fluide, ce qui n'est pas vrai puisque la pression dans un fluide près de la Terre varie avec la hauteur. Ce principe s'applique plutôt au changement de pression. Supposons que de l'eau soit ajoutée dans un contenant cylindrique de hauteur (H) et de section transversale (A) qui a un piston mobile de masse m. L'ajout de poids (mg) au sommet du piston augmente la pression au sommet de mg/A, puisque le poids supplémentaire agit également sur la surface (A) du couvercle.

Selon le principe de Pascal, la pression en tous points dans l'eau change du même montant, mg/A. Ainsi, la pression au fond augmente également de mg/A. Ainsi, la pression au fond du contenant est égale à la somme de la pression atmosphérique, de la pression due au fluide et de la pression fournie par la masse.

Ce texte est adapté de<a href="https://openstax.org/books/university-physics-volume-1/pages/14-3-pascals-principle-and-hydraulics"> Openstax, University Physics Volume 1, Section 14.3: Pascal's Principle and Hydraulics</a>.

La loi de Pascal

En 1653, le philosophe et scientifique français Blaise Pascal a publié « Traité sur l’équilibre des liquides », qui traitait de la ...

Education

Enseignement

JoVE Core

Physique

Unit 1

Unité 1

Fluid Mechanics

Mécanique des fluides

KEY TERMS AND CONCEPTS

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pascal’s principle in static fluids

Pascal’s principle explains how pressure changes move through a fluid that is not flowing. A fluid at rest is in static equilibrium. If the fluid is water, it is in hydrostatic equilibrium. In this state, the net force on any part of the fluid must be zero, or the fluid will begin to flow.

Blaise Pascal described this idea in 1653 in Treatise on the Equilibrium of Liquids. He showed that when pressure changes in an enclosed fluid, that change is transmitted without loss through the fluid and to the walls of the container. The principle applies to pressure changes, not to the total pressure being the same everywhere. In fluid near Earth, pressure still varies with height.

The total pressure in a fluid can come from more than one source. At a certain depth, pressure depends on the fluid depth and the pressure of the atmosphere. Inside an enclosed fluid, the moving atoms pass pressure along to all parts of the fluid and to the container walls. That is why any added pressure spreads undiminished.

A simple piston example shows this clearly. Imagine water in a cylindrical container with height H and cross-sectional area A, and a movable piston of mass m. If an extra weight of mg is placed on the piston, the pressure at the top increases by mg/A because the weight acts over area A. Pascal’s principle says the pressure throughout the water changes by the same amount, so the bottom pressure also rises by mg/A. The pressure at the bottom is then the sum of atmospheric pressure, fluid pressure, and the pressure from the added mass.

Pascal’s Principle in Static Fluids

characteristics of fluids

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pascal's law

Pascal’s principle explains how pressure changes move through a fluid that is not flowing. A fluid at rest is in static equilibrium. If the fluid is water, it is in hydrostatic equilibrium. In this state, the net force on any part of the fluid must be zero, or the fluid will begin to flow. Blaise Pascal described this idea in 1653 in Treatise on the Equilibrium of Liquids. He showed that when pressure changes in an enclosed fluid, that change is transmitted without loss through the fluid and...

application of pascal's law

Hydraulic Force Transfer with Pascal's Law

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key terms and concepts

Learn how pressure changes move through static fluids, why pressure is added in enclosed liquids, and how a piston changes pressure in water.

Pascal’s Principle in Static Fluids | JoVE K12

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Pascal’s Principle in Static Fluids

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