# What is Water pressure: Definition and 149 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.

View More On Wikipedia.org
1. ### Calculate the max speed at which a submarine rises/dives

I'm trying to figure out how I would calculate the rate at which a submarine (or any vaguely cylindrical object) ascends or descends in seawater given a certain buoyancy or change in buoyancy. For example, if my submarine is 2000 feet below sea level and weighs 393 metric tons (with empty...
2. ### B Why does increasing the height of a water tower increase water pressure?

Hello, I was wondering, for a fixed amount of water, why when the height of a water tower increases, the water pressure at the outlet of the pipe at the base of the tower increases ? I have often read on the internet that it would be caused by the weight of the water above the water at the base...
3. ### A cylinder with cross-section area A floats with its long axis vertical

Summary: A 5.0- cm -diameter cylinder floats in water. How much work must be done to push the cylinder 11 cm deeper into the water? F =Aρgx A 5.0- cm -diameter cylinder floats in water. How much work must be done to push the cylinder 11 cm deeper into the water? F =Aρgx x being the...
4. ### Question regarding water pressure and slopes

I have a question about water pressure PSI regarding the presents/lack of slopes. If two identical pressure sensors are set up on the ocean floor at the same depth. One being surrounded by a cone of ramps increasing in height moving outwards away from it. The second sitting on a flat plain...
5. ### Hydraulic Losses Through a Pipe

I am trying to estimate the pressure loss from a tap to a piece of equipment we are feeding water to. I have the pressure on the 12" ductile line. I have the friction losses in the different pipe sizes (1",1.5", and 2") for the service line. I also have the losses through the 1" meter. The only...
6. ### How to calculate water pressure drop in cooling tower piping system?

When calculating water pressure drop in chilled water pipisystem (closed circuit) we always use Hazen Williams equation as follow:- but in case of calculating water pressure drop in cooling tower piping system (open circuit), shall we modify something in Hazen Williams equation or shall we use...
7. ### I Issue calculating water pressure due to the constriction of water flow

For an experiment where I must be able to control the pressure i attached to a syringe a 'chamber'. The inner diameter of the syringe is 19.3 mm and i will fill water to 17 cm of the syringe bottom (i call this P1), the spout has a inner diameter of 2 mm and a length of 2 mm (i call this P2) and...
8. ### Force from Water Entering a Pressurized Tank with No Relief Valve

Hello all, I am trying to understand how a force at the opposite wall from water entering a pressurized air (atmospheric pressure) tank, and for this discussion it is rigid, with no relief valve to displace the compressed air can be deduced. I have created a simple illustration and believe this...
9. ### How Does Water Impact Force Affect Submerged Air-Filled Objects?

I am interested in conceptualizing the impact force of water against submerged objects that contain atmospheric air. The scenario is a bit much for me to conceptualize alone, so I joined PF to ask the experts in this community. Thanks!
10. ### Water Pressure and Different Pipe Sizes

Started an irrigation project. There are 4 points in this irrigation system; A, B, C and D. The main water line to the house is 1" diameter pipe. (Point A) The distance from Point A to Point B is approximately 30 feet. Here at Point B the pipe size is reduced down to 3/4" pipe. The distance...
11. ### Water pressure affects air pressure

In the movie The Abyss an oil rig crew works and lives at the bottom of the ocean in a deep sea structure. There is a compartment where there is an opening in the floor allowing the crew to lower a submersible craft without going through any kind of air locks etc. We all should know from high...
12. ### Plumbing Compressed air powered water pressure

Hi there, I have a few interesting problems that I have been exploring for a while now, but i quickly get beyond my level of knowledge of physics, so wondered if members of this Forum may be able to assist. One of the projects that we have been trying to solve is how to maintain a decent quality...
13. ### Water Pressure at the tap and practical Bernoulli equation

Hello, I think I understand how Bernoulli equations works but I am clearly uncertain on some aspects of its application. For example, let's look at the figure below: 1) The static pressure is ##60## ##psi## from the city water supply. There is not flow (tap closed) so the pressure at the...
14. ### Water Pressure and 2 dimensional motion

$$H = \frac { V^2 - V_0^2 sin \Theta} {-2g}$$ $$H = \frac {V_0^2 sin \Theta} {2g}$$ So, I need to calculate ## V_0 ## I'm thinking about pressure. $$P = \rho g \Delta h$$ $$\Delta h = h - L sin \Theta$$ $$F_A = P S_A$$ $$F_A = P S_B$$ Dead End here...
15. ### Water pressure question involving pipe, flexible hose and a filter

Summary: water pressure issues what happens when you take water from a 3/4 inch pipe copper to 1/2 inch flexible braided hose through a filter for a 3/4 pipe back through a flexible braided hose 1/2 inch tube to 3/4 inch copper pipe?
16. ### Rank the faces in order of decreasing water pressure

I assumed that the same magnitude of force acts on all sides of the box. Since A had the smallest area, I ranked P(A) as having the largest pressure, followed by P(B) having the second largest and P(top) and P(bottom) having the same pressure at third largest each. However, the ranking I...
17. ### Calculate lateral force/pressure of a body water

So I'm planning to build an above ground concrete fish pond. The size of the inside of the pond will be (L)2000mm x (W)500mm x (D)500mm. What I want to know before I go any further is will the poured concrete walls hold the pressure of the water inside. So if I know the pressure of water I'll...
18. ### Cause of water pressure in pipework

Am I correct in saying that water pressure (in typical domestic heating system pipework) is achieved by deformation of the pipes rather than compression of the water? I believe water to be virtually incompressible, so the 3 bar (or whatever) pressure must come from the elastic stretching of the...
19. ### Estimation and validation of water pressure at nozzle

ρ I am trying to estimate and validate the pressure of water exiting a nozzle. For an unknown reason, the validation is consistently twice as high as the estimation. Here the approach: Estimation: I am using the dynamic pressure equation for the estimation: q = 1/2 * ρ * u2 where, q = dynamic...
20. ### Calculating water pressure and the required mass of water

Basically what I'm trying to do is calculate the amount of water it would take to generate a given pressure at the water tap. Or to put it more simply I'm trying to figure out where the water line is damaged, well more for fun then actually being practical. The water system is simply a well on...
21. ### Calculating water pressure in a horizontal pipe

Homework Statement Homework EquationsThe Attempt at a Solution Calculating water pressure using in a horizontal pipe Applying Bernoulli principle, ## p_a + \frac 1 2 \rho gh_a + \frac 1 2 \rho v_a^2 = p_b + \frac 1 2 \rho gh_b + \frac 1 2 \rho v_b^2 ## ## h_a = h_b, v_b = \frac {...
22. ### Is Pressure Constant in U-Tube Arms with Different Density Liquids?

A liquid in a U-tube maintains the same level in both the arms. When another liquid which does not mix with the first one is poured in it, the air interface with either of the liquids in both the arms will be at different levels. Considering a point at the top surface of liquid A, the pressure...
23. ### How Water Dept's of major metros maintain water pressure?

Small towns in America frequently have water towers in which water is kept in huge tanks hundreds of feet high within water towers. I suppose that some sort of pump pumps the water entering the water tower to the tank at the top. I suppose that water pressure is maintain in these small towns...
24. R

### Calculating Water Volume in a Tank Using Pressure Measurements

Homework Statement on a flat desk is an aquarium with a volume of 640 cm3 ,t's not full of water. The pressure to the bottom of the aquarium is 3 times bigger than to one side of it, how much water is in the tank? Homework Equations is the pressure, is the normal force, is the area of...
25. ### Can we accurately measure water pressure using DIY water towers?

I'd like to explore water pressure by having students build water towers out of both 2-liter bottles and thinner 1 liter bottles. 1. Assuming they build towers of the same height and fill them with the same type of water, we should see the same water pressure for identical heights within the...
26. ### Water pressure vs pressure drop

Hi guys, I know the difference between these two things but I'm struggling with something that I hope someone could help me with. What dictates the water pressure needed for a "system" to work? I would imagine that if you've calculated your system to have a pressure drop of 1 bar (for...
27. ### Is the water pressure below ocean waves constant?

If you are stationary say 10m below the ocean surface does the water pressure at your location vary with the waves. For example: When a wave crest is above you than means perhaps 12m of water is above you. Then a few seconds later a trough is above you so only 8m of water is above you. So you...
28. ### [Programming] How would I simulate water pressure?

Hey, this is my first time posting and I've been looking everywhere but can't find a decent water model. I hacked a program together to decently simulate water physics, but it's not nearly robust enough for what I need. So, in this world, everything is based on a grid. Any non-wall tile can...
29. ### Calculating Water Pressure in a Half-Full Sphere: A Simple Explanation

I've been wondering how I can find the pressure water exerts on a sphere it's in. As for cyllinders and pyramids, and prisms - the thing is extremely easy - you just take the one formula and put in numbers. What about a situation when we have a sphere whose radius is R, and it's half full with...
30. ### Water pressure and flow restricton - does size matter?

I'm trying to figure out how to best filter some liquids. A 5 gal bucket is filled with some filter medium (say sand on top 1/2 and fine charcoal on bottom 1/2). The liquid is slowly added at the top and gravity is used and vacuum may be used at some point with a complete seal along the bottom...
31. ### Centrifugal pump restricted output

I am also constructing a small boat as a test bed for a much larger houseboat. If we forget about practicality issues... and accepting that my BS econ degree from the 60's isn't helping me much, I have a simple question with a difficult answer I guess. 2 stage centrifugal pump. (Standard...
32. ### L-shaped tank problem; forces due to water pressure

Homework Statement HELP! L-shaped tank problem! figure: http://www.webassign.net/hrw/hrw7_14-33.gif The L-shaped tank shown below is filled with water and is open at the top. (a) If d = 7.0 m, what is the force on face A due to the water? (b) What is the force on face B due to the water...
33. ### Calculate pressure on surface moving in water

Hello bright minds, I have a practical problem for which I need help solving, and I'm sure someone could help. I am wanting to place a pick up (sort of a backwards facing venturi type structure) under my kayak to fill up and supply a box with fresh water for my live baits. I would like to know...
34. ### B Does water pressure decrease in zero gravity?

me and my friend were talking on facebook and we couldn't think of an answer to the question, would water pressure decrease in zero G, you can see how far along we got before getting stuck in the picture belowhttps://www.physicsforums.com/attachments/105576
35. ### How to calculate pressure in a bottomless aquarium

How do I calculate glass thickness on a bottomless aquarium where air pressure is holding the water up. Example: 18"x18" by 36"' high closed top. 6" of the aquarium is submerged in a pond. Thanks.
36. ### 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...
37. ### How Can I Increase My Lawn Sprinkler System's Flow Rate?

I have a DIY project for a lawn sprinkler system but my flow rate is insufficient : if my setup is to work properly, the sprinkler manufacturer suggests a flow rate of 2880 litres per hour at a pressure no less than 2 psi. I measured the flow rate of my current garden faucet, which is connected...
38. ### How Can I Create Water Pressure in a Vessel Without a Standard Pump?

Hi there all physics geniuses. I come looking for help. I need to create water pressure in a vessel in the easiest possible way. And not by using a standard manual pump to pump in air. I've come up with a syringe-spring type system but it's flawed as the spring will rust... Also I've...
39. ### Is the water pressure of a cone greater than a cylinder?

is the water pressure at the bottom of a cylinder tank full of water more than the water pressure at the bottom of an upsidedown cone tank full of water?? If so, what eqauation could be used to find the pressure at the bottom of the cone?
40. ### Water Pressure Calculation (Limited Information)

Is it possible to find the pressure of water that leaves a pipe of certain area/diameter given only the flow rate of the water itself? OR the requires piping diameter/area given the pressure that I desire. I'm trying to design a system that requires relatively high pressure (for spraying)...
41. ### How Do You Calculate Pressure in Supercritical Water Syntheses?

Hello All, I am doing supercritical water syntheses in a sealed reaction container. I am looking for a way to calculate the exact pressure inside the reaction vessel as a function of the fill level and the temperature. This is to make sure I stay within the safe limits of my reaction vessel.
42. ### Increasing water pressure without increasing pump output

I am curious as to whether a nozzle at the end of a pipe that is completely submerged in water and has a pressurized flow being pumped through it in a closed condition can increase the amount of flow and pressure of the water in a pipe fixed to the exit side of that nozzle if the nozzle uses the...
43. ### How Is Total Pressure Calculated in Water?

Homework Statement Assuming g = 10 ms^-2 and the volumetric mass for water is 10^3 kg.m^-3 and the air pressure is 10^5 Pa, the total pressure on a point inside the water that's in equilibrium with a distance of 2m from its free surface is: A. 0.8 * 10^5 B. 1.002 * 10^5 C. 1.2 * 10^5 D...
44. ### Water pressure drop when 1 pipe splits into 3

Hi, what happens when I have a single pipe with pressure 1bar. I split this pipe into 3 equal pipes with equal diameter. What will be my pressure at the ends of these 3 equal pipes ? From what I have been reading on the internet it seems that the pressure will be the same on the 3 equal...
45. ### Water Pressure, small inlet vs. large outlet

If there is a "sewer box" (2' x 2' x 2') with a 8" drainage inlet pipe into it and it has a 18" drainage outlet pipe to discharge water entering into the sewer box and the large 2' x 2' grate opening at the top...IF the entire sewer box is inundated with storm water, will the incoming water thru...
46. ### Mammals deep underwater, water pressure, & implications

Large ocean/sea mammals, say a blue whale, are able to withstand large water pressures underwater, and I read that they're able to do so for a number of reasons, one of which is that the air cavities are thought to fill with water. Is it this equalization of pressure that allows whales to deep...
47. ### Water Pressure and Internal (Air) Pressure

If you have, say, two tubes of different internal pressures submerged to a given depth (for sake of the example, let's just say 1,000M underwater or 100 ATM), will the smaller internal air pressure tube experience a greater relative force from the water pressure? The water pressure on both tubes...
48. ### Water Pressure Homework Problem

Homework Statement A person swim to certain depth in the ocean where the density of sea water is 1025 kg/m3. he does not have sophisticated equipment but he used an empty tube, the tube is L = 45.4 cm long and shaped like a cylinder. He wets the sides and then puts some sand in and shakes it...