What is Pascal's principle: Definition and 30 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. C

    I Hydrostatics: Pascal's principle and ocean depth

    Hello everyone! I've been learning about hydrostatics and one thing that I've heard is that the pressure is the same throughout confined incompressible fluids, this is one of the reasons hydraulics work, because when you have the same pressure per square meter, you can change the mechanical...
  2. G

    Understand Pressure in Fluids: Conceptual Guide

    I'm looking for a conceptual understanding of pressure in fluid. According to what I've gathered, in static fluid, the pressure at any point in the fluid depends on the depth within the fluid, because there is more fluid weighing down on an object the deeper into the fluid it is. However, for...
  3. 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...
  4. E

    When is Pascal's Principle applicable?

    Homework Statement Which of the following statements about Pascal’s principle is true? A. It is valid only for incompressible fluids B. It explains why light objects float C. It explains why the pressure is greater at the bottom of a lake than at the surface D. It is valid only for objects that...
  5. DevonZA

    Hydraulic jack - Pascal's principle

    Homework Statement Homework Equations P1=P2 P=F/A F=PA F1/A1=F2/A2 F2 = F1(A2/A1) F2 = W(A2/A1) W=mg W=F*d The Attempt at a Solution A1= pi/4 * d2 = pi/4 * (0.15)2 = 0.0177m2 A2 = pi/4 * d2 = pi/4 * (0.05)2 = 0.00196m2 P1=P2 P=F/A F=PA F1/A1=F2/A2 F2 = F1(A2/A1) F2 = W(A2/A1)...
  6. Isaac0427

    Pascal's Principle vs. Bernoulli's Principle

    Hi, There is a basic problem I am having with fluid dynamics that has been really confusing me. I have been told that as a result of conservation of energy and Pascal's principle, for an incompressible fluid Pin=Pout, or pressure is constant. However, pressure is not necessarily constant in...
  7. A

    Pascal's Law Problems

    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

    Liquids: Pascal's Principle and fluid collisions

    Take a U-shaped piece of pipe, standing upwards. Fill the bottom part with liquid and leave the 'prongs' open. Now slam a parcel of liquid into one end at high speed. The other end will experience some momentum exchange and go pushed upwards. Now take the same test case and add some piping...
  9. T

    Centripetal Force and Pascal's Principle

    I am trying to reconcile what I understand about Pascals Law in Fluid Statics and Centripetal Force in Fluid Dynamics In fluid statics pressure always acts normal to the wall . The explanation I have seen https://www.physicsforums.com/threads/fluid-mechanics-and-perpendicular-force.733437/ Is...
  10. J

    B Struggling to understand a consequence of Pascal's priciple

    Suppose there are two vessels filled with water up to the same height: If I understand pascal's principle, the pressure in the bottom of both vessels should be the same. But the right one has more weight, so isn't the force on the bottom greater and therefore there is more pressure there?
  11. Ravi Singh choudhary

    What pressure not increases if I seal the container?

    CASE1: A container with some water is open to atmosphere, pressure is definitely atmospheric, no somehow I put cover over it and sealed it also. Pressure would increase because new equilibrium will establish between water and its vapour so pressure will increase in the closed container. CASE2...
  12. M

    Fluid mechanics - Pascal's principle

    Homework Statement Mercury is poured into a U-tube as shown in Figure a. The left arm of the tube has cross-sectional area A1 of 9.4 cm2, and the right arm has a cross-sectional area A2 of 4.50 cm2. One hundred grams of water are then poured into the right arm as shown in Figure b. (b) Given...
  13. G

    High-pressure compression of liquids

    Hello, My memories of fluid mechanics are very rusty and therefore I was wondering if you could help me with this hypothetical problem. Let's say I want to generate very high hydrostatic pressures in a liquid (of order of 400 kbar). Would it be enough to do the following: take a rod weighting 1...
  14. B

    Pascal's Principle Homework: Pressure Variation w/ Height & Diameter

    Homework Statement A small tube is connected to the top of a larger one and the whole thing is filled with water. The small tube has height a and the larger tube has height b. What happens to the pressure at the bottom of the larger tube as (1) a is varied, and (2) a is held constant but the...
  15. Z

    Simple Conceptual Question Regarding Pascal's Principle

    Homework Statement There's a conceptual question I've encountered in my reading, wherein we're supposed to determine the validity of a statement: "According to Pascal’s principle, if you increase the pressure enough so that the force at one end of an oil-filled tube increases by 10 N, the force...
  16. H

    Piston Question: Have solution, don't understand rationale

    Homework Statement The drawing below shows a hydraulic chamber in which a spring (spring constant = 1580 N/m) is attached to the input piston (A1 = 15.3 cm2), and a rock of mass 41.9 kg rests on the output plunger (A2 = 66.6 cm2). The piston and plunger are nearly at the same height, and each...
  17. E

    Pressure in Liquids and Pascal's Principle?

    Okay, so Pascal's Principle (as copied from Wikipedia): A change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid. From what I've gathered, this means that pressure in liquids act in all directions, so if you press a closed...
  18. F

    Pascal's principle hydraulic lift with torque involved

    Pascal's principle hydraulic lift with torque involved(need help with lever) Homework Statement A hydraulic jack is used to support a mass which has a mass of 30.7 kg. The mass is supported by piston 2 which has a mass of 0.250 kg and an area of 40.2 cm2 . A force is applied by the lever on...
  19. M

    Pascal's Principle with Hydraulic Pumps

    Homework Statement A hydraulic can crusher is shown in the figure. The large piston has an area of 8m2 and exerts a force F2 of magnitude 2x106 N on the cans. Calculate the magnitude of the force F1 exerted by the small piston (area 10cm2) on the fluid. Do not ignore that the large pistons...
  20. S

    Pascal's Principle on piston

    Homework Statement Imagine a hydraulically operated dentist's chair having a mass of 200kg, and in it is stiing a 54.8kg patient. The large piston below the chair has 5cm(diameter), while the small piston, moved by a pedal on which the dentist steps, has 1cm(diameter). What's the pressure in...
  21. Z

    Understanding Pascal's Principle: Water Dispenser for Pets

    I can't seem to wrap my ahead around this question! Please help me understand. A water dispenser for pets has an inverted plastic bottle. When a certain amount of water is drunk from the bowl, more water flows automatically from the bottle into the bowl. The bowl never overflows. Explain the...
  22. C

    Fluids - Pascal's Principle / Negative vs Positive

    Homework Statement The handle of a hydraulic jack is 15 cm long and is pivoted 2.5 cm from the input piston which has a radius of 0.60 cm. The output piston has a radius of 1.2 cm. What weight could be lifted by the jack if the person pushing on the handle is to exert no more than 110 N of...
  23. J

    Basics of pressure and pascal's principle

    I've being studying fluids and pressure, but want to clarify something. Take a rough example of a force applied on a fluid/gas is it correct to say that from 'P + pgh' one can say that as the volume and height increases or with these increasing layers there is more force been 'packed' behind...
  24. L

    Hydraulic Brake Fluids: Comparing Liquid X and Y

    Liquid X is denser than liquid Y but both have the same compressibility. In a vehicle hydraulic brakes, which liquid is more suitable to be used as the hydraulic brake fluid and why ?
  25. J

    Discovering Pascal's Principle: Solving Hydraulic Press Problems | Homework Help

    [SOLVED] Pascal's Principle help. Homework Statement A piston of cross-sectional area a is used in a hydraulic press to exert a small force magnitude f on the enclosed liquid. A connecting pipe leads to a larger piston of cross-sectional area A. 1. What force magnitude F(2) will the...
  26. P

    Pascal's Principle? Are my solutions correct?

    (a) If a 22 pound baby sits atop a 1 ft^2 piston that is connected to a 10 ft^2 platform via sealed, water filled pipes, how heavy and massive of a car can the baby's weight lift (answer in pounds, Newtons, and Kilograms)? (b) If the baby's initial height on the piston is 10 ft, how high...
  27. P

    Calculating Force/Mass Using Pascal's Principle for Baby-Lifting Car

    (a) If a 22 pound baby sits atop a 1 ft^2 piston that is connected to a 10 ft^2 platform via sealed, water filled pipes, how heavy and massive of a car can the baby's weight lift (answer in pounds, Newtons, and Kilograms)? (b) If the baby's initial height on the piston is 10 ft, how high...
  28. A

    Pascal's Principle Lab Idea for AP Physics BC

    hi, I'm new to this forum and i hope that you guys can help me with this and also in the future, i am currently taking ap physics bc. i need an idea for a lab on pascal principle (F2/A2) = (F1/A1), i was thinking about replicating a hydraulic car lift, but how would you measure the force...
  29. C

    Pascal's Principle Problem

    A piston of cross-sectional area "a" is used in a hydraulic press to exert a small force of magnitude "f" on the enclosed liquid. A connecting pipe leads to a larger piston of cross-sectional area A. (a) what force magnitude F will the larger piston sustain without moving? (b) If the piston...
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