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

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

Zasada Pascala mówi, że jeśli zmieni się ciśnienie w zamkniętym płynie, zmiana jest przenoszona na cały płyn i na ścianki pojemnika bez zmniejszania wielkości.
Aby zrozumieć tę zasadę, rozważ wielodyszowy pistolet na wodę o polu przekroju A wypełniony wodą.
Gdy tłok jest dociskany z siłą F, odpowiednia zmiana ciśnienia F/A jest przenoszona przez całą objętość wody i dociera do każdej dyszy.
Woda uwalnia się pod tym samym ciśnieniem przez każdą dyszę, zgodnie z zasadą Pascala.
Biorąc inny przykład, niech beczka zostanie podłączona do długiej cienkiej rury, przez którą wlewa się wodę.
Gdy beczka jest pełna i wlewa się do niej dodatkową ilość wody, ciśnienie wywierane przez wchodzącą wodę gwałtownie wzrasta w całej jej objętości w beczce, powodując jej wyciek ze wszystkich stron.

prawo pascala

W 1653 roku francuski filozof i naukowiec Blaise Pascal opublikował „Traktat o równowadze cieczy”, w którym omawiał zasady działania płynów statycznych. Płyn statyczny to płyn, który nie jest w ruchu. Kiedy płyn nie płynie, mówimy, że znajduje się on w równowadze statycznej. Jeżeli płynem jest woda, mówimy, że znajduje się ona w równowadze hydrostatycznej. W przypadku płynu znajdującego się w równowadze statycznej siła wypadkowa działająca na dowolną część płynu musi wynosić zero; w przeciwnym razie płyn zacznie płynąć. Pascal zaobserwował, że zmiana ciśnienia wywieranego na zamknięty płyn przenosi się w niezmienionym stanie po całym płynie i na ścianki jego pojemnika. Co więcej, zasada Pascala implikuje, że całkowite ciśnienie w płynie jest sumą ciśnień z różnych źródeł. Na przykład ciśnienie płynu na określonej głębokości zależy od głębokości płynu i ciśnienia atmosfery.

W zamkniętym płynie, ponieważ atomy płynu mogą się swobodnie poruszać, przenoszą ciśnienie na wszystkie części płynu i na ścianki pojemnika. Jakakolwiek zmiana ciśnienia jest przenoszona w niezmienionym stanie. Należy zauważyć, że zasada ta nie mówi, że ciśnienie jest takie samo we wszystkich punktach płynu, co nie jest prawdą, ponieważ ciśnienie w płynie w pobliżu Ziemi zmienia się wraz z wysokością. Zasada ta dotyczy raczej zmiany ciśnienia. Załóżmy, że do cylindrycznego pojemnika o wysokości (H) i polu przekroju poprzecznego (A) dodano trochę wody, wyposażonego w ruchomy tłok o masie m. Dodanie ciężarka (mg) na górze tłoka zwiększa ciśnienie na górze o mg/A, ponieważ dodatkowy ciężar działa również na powierzchnię (A) pokrywy.

Zgodnie z zasadą Pascala ciśnienie we wszystkich punktach wody zmienia się o tę samą wartość, mg/A. W związku z tym ciśnienie na dnie również wzrasta o mg/A. Zatem ciśnienie na dnie pojemnika jest równe sumie ciśnienia atmosferycznego, ciśnienia płynu i ciśnienia wywieranego przez masę.

Ten tekst jest adaptacją <a href="https://openstax.org/books/university-physics-volume-1/pages/14-3-pascals-principle-and- hydraulika">Openstax, University Physics, tom 1, sekcja 14.3: Zasada Pascala i hydraulika</a>.

Prawo Pascala

W 1653 roku francuski filozof i naukowiec Blaise Pascal opublikował "Traktat o równowadze cieczy", w którym omówił ...

Education

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Unit 1

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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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density

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variation of atmospheric pressure

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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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excess pressure inside a drop and a bubble

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buoyancy

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energy conservation and bernoulli's equation

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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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