What is Pascal's law: Definition and 25 Discussions

Pascal's law (also Pascal's principle or the principle of transmission of fluid-pressure) is a principle in fluid mechanics given by Blaise Pascal that states that a pressure change at any point in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere. The law was established by French mathematician Blaise Pascal in 1653 and published in 1663.

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  1. brotherbobby

    Understanding Pascal's Law: Why is Force Greater in One Cylinder Than the Other?

    Answer : Using Pascal's law, this is my answer : ##\color{blue}{\boxed{\vec F_a = \vec F_c < \vec F_b}}##. Reasoning : Forces ##F_a## and ##F_c## are equal because the pressures required at the two cylinders for case (c) is the same as that required in (a). It doesn't matter how many of those...
  2. G

    I Pascal's law (fluids): Derivable from fundamental laws?

    Hi. Pascal's law states that static pressure in a confined incompressible fluid without gravity is the same everywhere. Is this law derivable from more fundamental laws? Some thoughts: Is Pascal's law part of the definition of the liquid state? If the liquid operates between two hydraulic...
  3. Logic hunter

    B How does liquid starts moving when there is Pascal's law

    Consider a conventional U-tube with both the vertical tubes having the same uniform cross section area A and the horizontal tube of length L, connecting those tubes containing an ideal liquid. Now the free surfaces in both the vertical tubes will be at the same height and will have pressure...
  4. R

    When to apply Pascal's Law vs Bernoulli's equation

    Hello, I was solving a problem regarding pressure at different elevations. The question regarded water flowing through a pipe which travels up 5 meters. I used Pascal's Law (p = p(initial) + rho*g*h : rho is density of fluid, g is gravity and h is the height) and came up with an answer...
  5. I

    Hydrostatics, Length of a mercury column

    Homework Statement What will be the length of mercury column in a barometer tube, when the atmospheric pressure is 75 cm of mercury and the tube is inclined at an angle of 60° with the horizontal direction? Homework Equations Pascal's Law The Attempt at a Solution l ⋅ sinϑ = h l = h / sinϑ l...
  6. I

    Hydrostatics, find length of kerosene column in U tube

    Homework Statement A glass tube is bent into a U shape. Water is poured into the tube until it sands 12 cm high on each side. Kerosene (density = 870 kg/m3) is added slowly to one side until water on the other side raises 5 cm. What is the length of kerosene column? Homework Equations (ρhg)1 =...
  7. A

    How Do Hydraulic Systems Apply Pascal's Law?

    Homework Statement The large cylinder in a hydraulic press has 3 times the surface area of the small cylinder. What force should be applied to the small cylinder to create a lifting force of 7200 Newtons In a hydraulic-brake system, a force of 25 N can be applied to a surface area of 5 cm^2...
  8. L

    Pascal's law and kinetic energy in pipes

    If you have a U-shaped pipe like the attached image, with more fluid in the left column than the right, then the fluid will level out basically because of Pascal's Law. Force on the fluid is exerted on every part of it in equal direction etc.. So when the fluid levels itself it flows across to...
  9. Dileep Ramisetty

    I Is my approach for pascal's law wrong?

    In hydraulic lift utilising pascal law, larger piston area is A1 and the smaller piston area is A2 mass in = mass out and volume in = volume out (in-compressible),so A1*x1=A2*x2 (let x1 and x2 are displacements of respective pistons) A1*V1 =A2*V2 (on differentiation gives continuity...
  10. physea

    I Is Pascal's Law Wrong? Debunking the Myth of Equal Pressure in Fluids

    In a fluid there is gravity exerted so we know that the lower layers have higher pressure. Does that prove that Pascal's law is wrong?
  11. P

    How Does Atmospheric Pressure Affect Measurements in a Torricelli Barometer?

    I have a question about Pascal law. Recenly I was studying and I found this image in my physics book - a copy of the barometer which Torricelli used in his experiment (this is a redraw): Where the blue thing is the fluid (mercury), while the black thing is the container. According to my...
  12. G

    How Does Pascal's Law Apply When Adding a Water Column to a Sealed Piston?

    I have some questions in regards to a diagram that has a twist to the regular set up that is usually used with demonstrating Pascal's law and pistons. In the diagram I have attached, if you added a column of water on top of the large piston which is sealed at the top from the atmosphere, there...
  13. G

    Does Pascal's Law Apply to a Sealed Fluid System with Gravity?

    If you have a structure like a large bike air pump (i.e cylinder, air hose at bottom, plunger etc) and you make the following adjustments: 1. insert the hose back at the top of the pumping cylinder (making it a cyclical system) 2. fill the cylinder with water so that there is no air in cylinder...
  14. B

    Hydrostatic pressure and consequences of pascal's law

    I've had a doubt about the following (somewhat contradictory) statements. 1) pressure applied to an incompressible fluid is equally transmitted at all points. 2) pressure at points at different heights in a fluid placed in a container in a gravitational field are different. Gravity applies a...
  15. V

    In-Depth Pascal's Law Explanation

    Problem: The general idea makes sense intuitively to me, but most sources I've found cite Pascal's Law merely as scientific fact with not much explanation. What I'm wondering is why pressure applied at one point in a fluid is transmitted undiminished to all other points? Is it a concept due...
  16. H

    Pressure in fluids and Pascal's law.

    I have a lot of confusion and I hope someone can help me in clearing my doubts. considering a right cylindrical container with a liquid filled in ,if we take two points, y1 and y2(near the bottom) 1) first of all I thought that pressure inside a fluid arose because of the weight of the fluid...
  17. J

    Pascal's law out of statistical physics

    Hi I wanted to get Pascal's law \Delta p= \rho g ( \Delta h) out of the context of statistical physics by the use of a partition function. I failed. Do you know how to solve this problem? Greetings
  18. L

    : Hydraulic Press & Pascal's Law

    Is there any way to deduce pascal law from Newton's laws? Another question: in a hydraulic press, with the smaller piston with A=1, and the other with A=2, the force in both shouldn't be the same? When the smaller piston goes down a distance d, the other piston goes up a distance d/2...
  19. L

    Proof Pascal's Law: Math Fluid Mech Homework Help

    Homework Statement My son was given a proof of Pascal's Law and told to learn it for his course in Fluid Mechanics. a. It was done with a prism. I cannot type in a link, but google: pascal law prism and pick the first link and scroll down half a page to pressure and you will see this proof. b...
  20. J

    Pascal's Law - Weight of Water Involvement

    Pascal’s Law states “pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the pressure ratio (initial difference) remains the same”. My question is, are the two scenarios that I have outlined the same? (see...
  21. L

    Pascal's law and variation of pressure with depth

    Homework Statement Pascal's law states that " The pressure in a fluid at rest is the same at all points if they are at the same height" Also we know " Pressure increases with depth" I get confused. When pressure increases with distance, how pressure is same at all points. Homework...
  22. E

    Pascal's Law - pressure inside the liquid vs. force needed to lift the liquid

    I'm going to steal a picture that was used in a different thread in this forum. [PLAIN]http://img821.imageshack.us/img821/7469/75687957.jpg (both containers are open at the top, and both contain water) I watched an MIT video of professor Walter Lewin, who used these very same...
  23. B

    Pascal's law, pressure, consequences

    Yes equations say its the same pressure, but its soooooooo non intuitive! Can you please explain, and try to near this problem to me, i can't sleep! [PLAIN]http://img821.imageshack.us/img821/7469/75687957.jpg How come the pressure at A and B is the same, although we don't have same...
  24. C

    Does Pascal's Law Apply to the Ocean?

    This isn't a math question really, and I'm really sorry if I put this in the wrong section. Still, I've been going over fluid dynamics in class and I have a question about Pascal's Law. It may be silly, but it's one that's been kinda bugging me. Pascal's Law says that any change in pressure of...
  25. G

    Pascal's Law - Containers filling up

    Homework Statement Homework Equations P1=P2 The Attempt at a Solution My first instinct is E), they are all equal. So the water fills up the bottom part slowly and it will fill up to the level of the containers equally (obviously). From there, the water will start filling the containers...
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