# 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. ### 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...
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### Fluid pressure at an interface

Suppose we have an incompressible, viscous sessile drop subject to a time-dependent pressure field ##p## on a substrate. Let ##\mu## be dynamic viscosity, ##u## be the fluid velocity field, ##\kappa_{1/2}## curvatures of the fluid surface, ##\sigma## surface tension, ##\hat n## normals to the...
3. ### 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. ### 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. ### 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. ### Equation Needed for Calculating Fluid Pressure In a Pipe

A friend is planning to utilize a local stream to create electric power. The source of the stream is a small pond. He plans to have a 5 inch pipe start at/near the bottom of the pond and this pipe will follow the stream approximately 1056 feet to a culvert where he wants to put the generator...
7. ### 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. ### Relation of shape of bottle to water pressure

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. ### 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. ### 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. ### 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. ### 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. ### 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. ### Fluid pressure on an object in open system

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. ### Understanding Fluid Pressure: Get Help Here!

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. ### 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. ### 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. ### 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. ### Fluid pressure close to an accelerating plate

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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### Calculating Force Exerted by Water on a Tilted Plate in a Tank

Hi I have a midterm study guide question. This one has stumped me for a while and probably the only one undone. Homework Statement Suppose there is a semi-circular plate of radius 5 ft that rests on its diameter and is tilted at 45 degree angle to the bottom of a tank lled with water to...
28. ### 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. ### 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. ### Fluid pressure problem and units confusion

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. ### Calc 2 Fluid Pressure problem setup

Homework Statement Calculate the fluid force of a right triangle with height 3ft and base 2ft submerged in water vertically and it's upper vertex at a depth of 4ft. Homework Equations F = w int(from a to b) y*f(y)dy The Attempt at a Solution I'm just not seeing how to set this...
32. ### Integration application, force due to fluid pressure

Homework Statement I'm working on a particular problem that involves the force on a face of a triangular prism under water. What I am wondering is if someone could explain how to find dA for the prism? If the prism is an equilateral triangle, then dA=\sqrt3dy doesn't it? My book is showing...
33. ### 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. ### Fluid pressure integral problem. Pretty easy, although I'm getting wrong answer

Homework Statement...
35. ### Fluid pressure in a U-shaped tube

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...
36. ### 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...
37. ### 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...
38. ### Multi Tube and fluid pressure

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...
39. ### 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...
40. ### How Is Fluid Pressure Calculated in a U-Tube Experiment?

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...
41. ### 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...
42. ### Calculating Air Column Length in a Capillary Tube Using Boyle's Law

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...
43. ### 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?
44. ### 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...
45. ### Calculating Piston Heights in a Car Lift: A Fluid Pressure Problem

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...
46. ### How Do You Calculate the Movement of a Hydraulic Lift's Input Cylinder?

Fluid pressure problem? please help! Homework Statement The input cylinder of a hydraulic lift has a diameter of 8.00 cm, and a bronze lion sits on a cylinder with 198.0 cm diameter. If the lion has a mass of 1395 kg, how far down does the input cylinder have to go to lift the lion 0.500...
47. ### Fluid pressure, energy and temperature

Hi everyone. This is my first post here... I want to create a numerical simulation in software, to solve the Navier-Stokes equations (Newtonian fluids, compressible and viscous flow) and I have some questions regarding fluids and their dynamics. (1) The Navier-Stokes equation for the...
48. ### Fluid pressure in different test tubes

Homework Statement okay, so what I've been asked to do is explain why a liquid reaches a higher altitude in a skinnier test tube than in a wider test tube. i've brainstormed ideas...but i can't find the one that deals with pressure and tension and stuff like that...stuff that deals with...
49. ### 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?
50. ### A question about fluid pressure

Homework Statement The deepest point in the ocean is in the Mariana Trench about 11 km deep. The pressure at the ocean floor is huge, about 1.13*10^8 Pa. a) calculate the change in volume of 1.00 m^3 of water carried from the surface to the bottom of the Pacific. b) The density of water at...