What is Fluid pressure: Definition and 53 Discussions

Pressure (symbol: p or P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled gage pressure) is the pressure relative to the ambient pressure.
Various units are used to express pressure. Some of these derive from a unit of force divided by a unit of area; the SI unit of pressure, the pascal (Pa), for example, is one newton per square metre (N/m2); similarly, the pound-force per square inch (psi) is the traditional unit of pressure in the imperial and U.S. customary systems. Pressure may also be expressed in terms of standard atmospheric pressure; the atmosphere (atm) is equal to this pressure, and the torr is defined as 1⁄760 of this. Manometric units such as the centimetre of water, millimetre of mercury, and inch of mercury are used to express pressures in terms of the height of column of a particular fluid in a manometer.

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  1. theycallmevirgo

    Intro text on building a small fluid pressure chamber?

    As stated in the summary, I'd like to design a chamber to store water under pressure. Nothing too powerful - basically at the level of a super soaker, maybe a little higher. The trick is, I want it to be powered and controlled electronically. But, I come from electronics land and know nothing...
  2. M

    Fluid pressure at an interface

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  3. S

    Fluid force at the end of a pipe

    Consider the very standard pipe problem used to calculate the force required to hold a pipe with a bend that has some fluid flowing through it, as shown in the image. We use Newton's second law of motion to calculate the external force required. However, why is there pressure acting into the...
  4. L

    Why does fluid pressure decrease with higher density in narrow pipes?

    So I was playing around with Fluid Pressure and Flow over on PHET animations and noticed something odd. When a fluid with high flow rate is going from a large pipe to a small pipe a lower density increases the pressure. And a higher density lowers the pressure in the narrow part of the pipe. My...
  5. G_Mallard

    Not sure Exactly what Pressure I am Solving for in this Form

    Hello all, I am posting this question here in this thread and not the homework thread since it is not a homework problem but something I have been working on myself. Let us imagine a fluid flowing through a pipe, we can measure pipe diameter and fluid velocity. The density of the fluid is also...
  6. R

    Equation Needed for Calculating Fluid Pressure In a Pipe

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  7. G

    Fluid Pressure & Force Calculus 2

    Homework Statement A marine biology observation pod is being designed. It will be submerged, with vertical windows of various sizes and shapes. Calculate the total force being exerted on each of the windows described below. Density of water is 1000 kg/m^3...
  8. A

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    So, I know that according to everything online water pressure is independent from everything except gravity, height, and density of fluid. The situation I'm talking about is slight different. Imagine a standard water bottle that angles inwards near the top. Now imagine a point on the side of...
  9. A

    Conceptual question, fluid pressure in a barometer

    Homework Statement I took a stab at the following question in a book: "In one observation, the column in a mercury barometer has a measured height h of 740.35 mm.The tem- perature is -5.0 C, at which temperature the density of mercury r is 1.3608 10^4 kg/m^3 .The free-fall acceleration g at...
  10. L

    Fluid Mechanics- inviscid fluid pressure in a pipe

    Homework Statement Water flows through a circular pipe with a 180° horizontal elbow and exits to the atmosphere through a nozzle as shown in Fig. Q3. The diameter of the pipe is 300 mm and the diameter of the nozzle exit is 160 mm. The density of water is 999 kg/m3 . The mass flow rate of...
  11. R

    Need help re: air pressure to fluid pressure

    Hi, I'm working on a project and need a bit of help, since I don't want to kill myself. My question is this: If I have a cylindrical tank (think a big scuba tank) half full of liquid, half full of gas (let's just say it's water/air) and start heating up the liquid, I know that pressure will go...
  12. Saumya Kar

    Difference between acoustic pressure and fluid pressure

    While the sound waves travel in a medium, let's say a fluid, what is the difference between fluid pressure and acoustic pressure ? Are these entities same?
  13. A

    Calculation of fluid pressure through water flowing pipe?

    HI. I'm confused in how to find pressure in horizontal Pipe theoretical. Pipe having 90mm dia and water flowing through 3m/s. If I'm insert one plate in pipe having surface area 'x', then how much pressure acting on the surface of plate by water? please explain me.
  14. T

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    Hello everyone, I have a physics question on pressure exerted by a fluid onto an object (see attachment). I would like to know how I can calculate the total pressure exerted on an object in a vessel by flowing fluid (water) with an open outflow. It has been too long since I took college...
  15. B

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    Homework Statement Homework Equations fluid pressure = fluid density * depth * gThe Attempt at a Solution My understanding is that fluid pressure at any two points at the same depth is equal, for a fluid at rest. But because one end is open, the pressure at point C is less than B and equal to...
  16. F

    Fluid pressure question in US units

    Homework Statement The ocean liner Titanic lies under 12500 feet of water at the bottom of the Atlantic Ocean. (The density of water is 62.4 lb/ft{}^3.) What is the water pressure at the Titanic? (Give your answer in both pounds per square foot and pounds per square inch.) Homework...
  17. A

    What Type of Pressure Valves Are Needed for an Underwater Flow Widget?

    If anyone can help it will be greatly appreciated. Im trying to figure out what type of pressure valves to use in an underwater flow widget. The widget is a cylinder with 1 inflow valve and 1 outflow valve. The cylinder is filled with colored water. As the cylinder moves through water I want...
  18. W

    Calculating Fluid Pressure in an L-Shaped Tank

    Homework Statement The L-shaped tank shown in the figure is filled with water and is open at the top. If d = 4.81 m, what is the total force exerted by the water (a) on face A and (b) on face B? image: http://edugen.wileyplus.com/edugen/courses/crs4957/art/qb/qu/c14/fig14_33.gif Homework...
  19. C

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    Hi all, I need to calculate the pressure in a fluid at some fixed distance from a flat plate which is accelerating (normal to its surface) through a fluid. If you assume the plate to be infinite (i.e. a rigid half-space), then I think the problem can be formalised as a one dimensional...
  20. Egregious

    Simple question about fluid pressure (medical injection)

    Hello, and thank you kindly for considering my question. Background: Medical needles come in gauges such that a smaller gauge represents a larger needle. Scenario: Doctor Jack says "18 gauge needles are best for this procedure", but Doctor Jane says "27 gauge needles are best because...
  21. A

    Fluid pressure homework help please

    The main water enters a house on the first floor. the line has a gauge pressure of 1.9x10^5Pa a) A faucet on the second floor 6.50 meters above the first floor is turned off. what is the gauge pressure of this faucet? b)how high could a faucet be before no water would flow from it even if the...
  22. G

    Question about fluid pressure

    Two questions: 1. Why is it that pressure exerted by fluids is not dependent on the amount of fluid around the point, only above? 2. Why is it that in deep wells, pump located underwater is better than a pump located on ground level?
  23. T

    Question: Understanding Fluid Pressure and Its Relation to Flow Speed

    Hey Everybody! It's my first time posting here, so please forgive any errors that might creep into this post. I'm a guy who loves physics. In fact, it has been my favorite subject ever since I can remember, and in physics, the field that attracts me the most is kinematics. Well...
  24. T

    Why the fluid pressure does not affected by the object submerged?

    As we know P=P_{0}+\rho gh If now I put an object of height h into the water, just completely submerged, why the pressure below the object not P=P_{0}+\rho_{obj}gh instead? Is it because it may not be in equilibrium or is it due to some other properties of fluid? Thanks!
  25. G

    Fluid Pressure Question (not a homework problem)

    It's spring break right now, so I thought I'd take the time to brush up on stat mech and thermo before classes resume next week... My question is this (Problem #1096 in "Problems and Solutions on Thermodynamics and Statistical Mechanics" Edited by Yung-Kuo Lim): A flask of conical shape...
  26. J

    Fluid Pressure Equation for 150 m3 Silo | Sensor Calibration and Display Reading

    Homework Statement A 150 m3 silo- a cylinder (12 m high) is used to store cream (density 850 kg m-3). An electronic pressure sensor (measures gauge pressure) is mounted 0.6 m up from the base of the tank, and a 0 to 100% display is used to indicate the level. It is not possible to sense the...
  27. N

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  28. R

    Calculate fluid pressure loss due to hole leakage

    I have a cylindrical pipe of internal diameter of around 5mm, say capped at one end with pressurised fluid flowing though the other opening. If I have holes at the wall of the pipe, am i able to calculate the pressure loss due to water squirting out through those side holes?
  29. K

    Fluid pressure (verification please)

    1. The water in a tank is at a gauge pressure of 267,018 Pa. If the bottom of the tank that has an area of 0.8 m2, what is the force on the bottom of the tank? 2. P=F/A; F=P*A 3. Converted Pa into 38.8psi for P (267,018/6890); Converted the Area into 103.7 in^2 (.8*10.8*12)...
  30. Y

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    Homework Statement Exercise Find the pressure at a depth of 10 m below the surface of a lake if the pressure at the surface is 1 atm. (Answer: With P0 = 1atm = 101kPa, ρ=103kg/m^{3}, and g= 9.81 N/kg, we have P = P0 + ρgh = 1.97 atm. The pressure at a depth of 10 m is nearly twice that at...
  31. D

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  32. D

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  33. H

    Archived Fluid pressure in a tank - manometer

    Homework Statement The level of benzene in a storage tank may fluctuate between 10 cm and 300 cm from the top of the tank. Since it is impossible to see inside the tank, an open-end manometer fluid is to be used to determine the benzene level. One leg of manometer is attached to the tank...
  34. O

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    This really isn't a homework question, I just need help understanding some concepts. For my physics course, we have a section called "tutorial" where we work out of a book answering questions. Now I am not quite sure how to answer this one. Refer to the image below for the questions...
  35. F

    Static fluid pressure. What did I do wrong?

    Homework Statement Calculate the depth h of mud for which the 3m concrete retaining wall is on the verge of tipping about its forward edge A. The density of mud may be taken to be 1760 kg/m3 and that of concrete to be 2400 kg/m3 The Attempt at a Solution So I made A actually at 1.5m down...
  36. Tclack

    Fluid pressure; inclined angle

    I can do vertically submerged fluid force problems. One portion of my book says: If a flat surface is immersed so that it makes an angle of 0 \leq \theta \geq \frac{\pi}{2} with the vertical, then the fluid force on the surface is given by: F=\int^b_a \rho h(x)w(x)sec\theta dx Can someone...
  37. O

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    Homework Statement Now two fluids are placed in the same tube (d). Both sides are open to the atmosphere without pistons. One fluid is water and the other (on top of the water in the left branch of the tube) is an oil of unknown density. l = 135mm and d = 12.3mm. What is the density of the...
  38. P

    Pressure increases as density increases.

    Homework Statement Water contracts when cooled (at least above 4 °C). A beaker of water is cooled from 50 °C to 20 °C. The pressure at the bottom of the beaker increases. Does the pressure increase or decrease as temperature decreases The absolute pressure at the bottom of a cylinder filled...
  39. L

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    1. The locations of the two caps at equilibrium are now as given in this figure. (Part D figure) The dashed line represents the level of the water in the left arm. What is the mass of the water located in the right arm between the dashed line and the right cap? 3. p - p_0 +rho*g*d...
  40. L

    Question on Fluid Pressure in Pipes

    Hi, I was doing my fluid mechanics howework, and there was a question that I couln't quite answer. Assuming that the integral of the axial momentum remains constant along the pipe cross section, the pressure drops uniformly along the pipe length. (Contrary to the Bernulli equation where the...
  41. M

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    Homework Statement A uniform capillary tube (with one end sealed) contains air trapped by a mercury thread 40mm long. When the tube is placed horizontally, the length of the air column is 36 mm. When placed vertically, with the open end of the tube downwards, the length of air column is now x...
  42. J

    Fluid pressure physics homework

    A 0.800 m-diameter vat of liquid is 2.70 m deep. The pressure at the bottom of the vat is 1.20 atm. What is the mass of the liquid in the vat?
  43. M

    Conceptual Pressure Question: Fluid Pressure in a U-Tube

    Homework Statement A U-tube is filled with water, and the two arms are capped. The tube is cylindrical, and the right arm has twice the radius of the left arm. The caps have negligible mass, are watertight, and can freely slide up and down the tube. A one-inch depth of sand is poured onto the...
  44. T

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    Homework Statement A car lift has two pistons. The one that lifts the car has an area of 2 meters squared, the one that is pushed down has an area of 1 meter squared. If a car weighing 2000kg is to be lifted 2m, how far must the smaller piston be pushed down? The pistons are of negligible...
  45. A

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  46. S

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  47. B

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  48. K

    Calculating Hydrostatic Force on Bolts in a Dam Plate

    A rectangular plate is covering a hole in a dam. I've calculated the hydrostatic force acting on it, but how do I find the force that acts on each of the four bolts in the corners of the plate?
  49. R

    A question about fluid pressure

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