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.

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  1. E

    Water pressure in multiple tanks

    hi - i am new so forgive any errors. question is this. if a number of water tanks are stacked one on top of the other. and each share the same downpipe with a tap at ground level. When the tap is opened which tank will drain first and why? many thanks.
  2. A

    Inrease in water pressure as a function of temperature under constant volume

    Hi all. I have a large pipe network that can hold say 1000 cubic meters of water. The pipe network is closed and pressurized to say 10 barg at 25 deg C. If the temperature of the water increases to 55 deg C, how much will the pressure in the pipe network increase? I would appreciate if you...
  3. P

    Oil spill: Water pressure VS. oil pressure

    Hello all, It's my first post. I'm french Canadian so I may make grammar mistakes in English :-) This is a question I'm asking me since yesterday. It's about the oil spill in the Gulf of Mexico. The oil and gases are less dense than the salted water. The breach is at about 1500 meters...
  4. D

    How can water pressure be measured in m

    How can water pressure be measured in "m" Hi I need to understand how minimum residual pressure can be measured in meters. At least I think its meters. The specific sentence in the abstract is: "The South African civil engineering fraternity has grown to accept 24 m as the design criterion...
  5. A

    Water pressure in a tank problem

    Homework Statement A water pipe feeds a water tower with water. The tower is 15 metres tall. If the water is to flow into the tank what is the minimum pressure of water at the bottom of the tower? Assume litre of water = 1 kg Assume 1 BAR = 1kg cm-2 Homework Equations P = p g h ? The...
  6. C

    Calculating Water Pressure on Water Barrel Walls

    Can anybody help? I am not a physics or science expert. So be patient and laymens terms please. I am trying to calculate the pressure of water on the side walls of a water barrel that I make to store rain water collected from roofs. The barrels have an inside bladder that is clad with...
  7. V

    Calculating water pressure from bernouliis equation

    A power station is supplied with water from a reservoir. A pipeline connects the reservoir to the turbine hall The flow of water through the pipeline is controlled by a valve which is located exactly 500 metres below the surface of the water in the reservoir. The pipeline is 0.30 m in...
  8. S

    Building an ice rink - question about water pressure exerted on a wall

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  9. D

    How Does Water Pressure Change with Depth and Altitude?

    Homework Statement At the surface of a freshwater lake the pressure is 106 kPa. (a) What is the pressure increase in going 34.5 m below the surface? (b) What is the approximate pressure decrease in going 36 m above the surface? Air at 20°C has density of 1.2 kg/m3. Homework Equations...
  10. C

    Understanding Water Pressure Zones: A Curious Chick's Question

    Hello, Chitose the curious chick again. This is not my home work, but something I keep wondering since I watch movie 'The Abyss'. http://en.wikipedia.org/wiki/The_Abyss" first the picture. (I draw it with photoshop, hope you guys don't get confuse) And the question. I wonder...
  11. S

    Bell shrinking due to water pressure

    A bell of diameter 3m and bulk modulus of 14x1010N/m2 is toss into the ocean. By how much did the diameter decrease as it sank to a depth of 10km? The bell is assumed to be a sphere of diameter 3m. Well o what i did was to calculate the pressure at the depth of 10km so P=Po+\rhogh which gives...
  12. S

    Solving for Water Pressure and Equilibrium in a Tube with a Piston

    Homework Statement Not exactly sure how to post this but i will give it my best. You have a tube and for simplicity sake let's say it is 1 ft by 1ft square. The tube is 42 inches tall. This tube is full of water and has a water tight piston at the top that is 1 ft by 1 ft. At the bottom...
  13. J

    Water Pressure Calculation with atmospheric pressure corrections

    I am looking for a formula to let me obtain a pressure reading comparison for two different tests based upon the following information: I have a given flow rate in liters / minute. (same for each test) I know the size of the orifice that the water is flowing through. (same for each test)...
  14. L

    Simple question about water pressure in a cylinder

    Hi all, I was asked today by a friend a simple question but couldn't answer so I'm asking you. Let's assume we have a vertical cylinder full of water, what is the pressure on the sides of the cylinder? If it was the pressure downwards it simply L*g*rho but to the sides I'm not sure... 10x a...
  15. P

    Water pressure, volume, temperature

    Hi There Can some one please help me find a table or chart that has accurate data for water pressures and temperatures at constant volume. I'm testing how much pressure an aerosole canister can take by filling it with water, sealing it and applying a flame tourch. I know how much heat the...
  16. S

    Calculating Water Pressure: Hazen-Willams Formula for 24' Tank & 650' Distance

    I have a water tank that is 24' tall. Water flows from the bottom of the tank thru a 8" plastic pipe for a distance of 650' down a hill for a elevation drop of 70'. What would be the expected water pressure at the bottom of the pipe given a flow of 20 gallons per minute? I've researched several...
  17. K

    Crazy water pressure formula implication?

    Hey everyone, I just thought of a mind-boggling "thought experiment": As a reminder, the formula for water pressure acting on an object due to weight is: (Water density)*(Acceleration of gravity)*(Depth of object underwater) Note that the shape of the container doesn't matter...
  18. B

    Solution: Solve a Water Pressure Dilemma

    I have a problem that 'seems' to defy physics. I've been told that when your mind and physics don't mesh, go with physics, so I will, but I'm not taking it well. Okay, here's the problem. I was building a 1000+ gal aquarium in my home. Eight feet long, six feet from front to back and 38 in...
  19. D

    Calculate water pressure coming out of a pipe

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  20. V

    Air Pressure and Water Pressure

    Homework Statement "At the surface of a freshwater lake the air pressure is 1.1 atm. At what depth under water in the lake is the water pressure 4.5 atm?" Homework Equations I used the equation Pgauge = Dgh The Attempt at a Solution I converted my atm to Pascals-->...
  21. O

    How Does Pipe Expansion Affect Water Pressure?

    Homework Statement Water flows at 6.1 m/s in a horizontal pipe with a pressure of 3 ´ 104 N/m2. If the pipe widens to twice its original radius, what is the pressure in the wider section? Give answer in Pascals. Homework Equations volume = length x area rate = volume / time rate =...
  22. R

    Velocity of a water jet given water pressure and diameter?

    I need to determine the velocity of a water jet. For example, if a garden hose is 1/2" in diameter and we assume that the water pressure is 40psi, what would be the water velocity (in ft/s) as it exits the hose (assuming no nozzle)? We know Pressure = force/area, but I want to know the...
  23. G

    Water Pressure and Equilibrium in Underwater Cylinders

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  24. S

    Can a Small Tank Solve the Problem of Fluctuating Water Pressure?

    hi i m new in this forum...n i have come to take some suggestion... i m plaaning to make a water supply which willl give some specified guantity supply(like 500 ml,250 ml) everytime...bt the main problem occurring is the water pressure in the outlet...the water pressure is not same all the...
  25. Redbelly98

    Electronics: using water pressure & flow analogy to explain voltage & current

    Electronics / electrical engineering forums often get questions from novices who have trouble understanding the concepts of voltage and current. Invariably, a more knowledgeable person will explain it by giving the standard analogy between electricity and water: voltage <--> water pressure...
  26. A

    How Does Water Pressure Affect Buoyancy in Different Submerged Objects?

    hi, I'm stuck on a homework task I've been given..help will be greatly appreciated:)) image link: img168.imageshack.us/my.php?image=image1vn3.jpg setup is as follows: image 1 . a tube (1ft diameter) submerged in water. tube is filled with air-filled balls( 1ft diameter) which tightly fit...
  27. Q

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  28. M

    How Do You Calculate Variable Water Pressure in Pipes?

    ive scanned about 200 closely relevant posts to make sure I am not one of those "here we go again" posts, but can find no basic water pressure formula. Specifically I need to calculate variable hypothetical water pressures (with a final conversion to GAUGE pressure) with a known INLET PSI...
  29. M

    Help me settle a bet about water pressure

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  30. C

    Formula for water pressure, flow and power

    I feel like this should be readily available, but I cannot find any information about it through google. I am trying to find a formula that will tell me the amount of energy necessary to inject water into a system at a given pressure. Put another way: I have a pipe of a known size and...
  31. H

    Gravity's Effect on Water Pressure in Orbit

    We all know that pressure inside a liquid is caused by its gravity and it is the product of the depth and weight density. So I just immagine if we have a sealed bottle full of water in the orbit, where the gravity is gone, is there any pressure of the water onto the bottle wall?
  32. L

    Is the relationship between water pressure and gravity a direct correlation?

    I hope this is the best sub-forum for this question: How direct is the relationship between water pressure and the weight of the water, as determined by the local gravity where the water is? In other words - let's say we have a submersible with a crush depth of 1000 feet on Earth. If we...
  33. B

    How Does Water Pressure Change with Velocity and Elevation in a Tapered Pipe?

    A water pipe having a 2.5 cm inside diameter carries water into the basement of a house at a speed of 0.90 m/s and a pressure of 170 kPa. If the pipe tapers to 1.2 cm and rises to the second floor 7.6 m above the input point, what is the (a) speed, and (b) water pressure, at the second floor...
  34. R

    Elasticity in high water pressure environment

    How does elasticity change in a high water pressure environment? For example, assume you drop a common rubber band in the ocean. As the rubber band sinks, water pressure increases on the rubber band. Excluding any change in temperature of the rubber band, how does the elasticity of the...
  35. C

    Understanding Water Pressure: Tips for Measuring Flow from a 250 Gallon Tank

    If there is anyone out there that can answer this it would be greatly appreciated. I am stuck with this one. At normal pressure of its own weight how can I determin the water pressure of water coming out of a 3/8ths in. nozzle out of a 250 gallon tank?
  36. I

    Calculating Water Pressure: A Puzzle to Solve

    To determine the pressure of water, you would use Force/Area. With a column of water. For example a 4 inch diameter column of water with 24 pounds of water in it. Equation would be 24/12.56637061. Would equal 1.909 psi. But if at the bottom of the column there was a 1 inch diameter tube. Would...
  37. P

    How Does Water Pressure Vary in Different Shaped Tanks?

    Tank A |...| |..h2o...| |..h2o...| |_h2o__| Tank B \.../ .\..h2o../ ..\.h2o./ ...\h2o/ Tank C .../...\ ../.h2o.\ ./..h2o..\ /__h2o__\ The three tanks shown above are filled with water to an equal depth. All the tanks have an equal height. Tank A has the middle...
  38. E

    Water pressure vs. area of an object

    I've been looking at this question for about 1 hour now, and cannot figure out the relationship between the distance an object is at the bottom of the ocean vs. its area... The question is: A solid copper ball with a diameter of 3.20 m at sea level is placed at the bottom of the ocean, at a...
  39. K

    Solving Water Pressure Problems: Guidance for Parts B and C

    Could anyone offer me some guidance on parts b and c of the following question? The pressure in a uniform pipe of flowing water is enough to hold up 4.00 m of water in an open, vertical tube as shown in Figure P.60. Assume that water is an ideal fluid. The pipe leads 3.00 m upstairs and...
  40. 2

    Water Pressure - Horizontal or Lateral

    Water weighs about 6lbs per gallon. So if one has a column of water, say, at 10 gallons, the pressure over an area is about 60lbs. This can be deduced to pounds per square inches. Question: How much pressure, per square inch, does water exert on a vertical wall such as a swimming pool...
  41. B

    How Does Water Pressure Change with Depth?

    Hi, I am lost with this problem. A bottle containig air is closed with a watertight yet smoothly moving piston. The bottle with its air has a total mass of 0.30kg. At the surface of a body of water whose temperature is a uniform 285 K throughout, the volume of air contained in the bottle is...
  42. B

    Calculate Water Pressure at Points 0-5 in a Siphon

    A siphon is used to empty a large vessel of water (see picture). Calculate/state the intial (absolute) pressures at points 0, 1, 2, 3, 4 and 5. http://img499.imageshack.us/img499/8104/siphon1oq.th.jpg P0 = 1.013 x 10^5 Pa - the pressure exerted on the water by the atmosphere P1 = Po +...
  43. S

    A few questions about water pressure, temp, and sound

    OK. I have done most of them correctly on my own, I need 2 checked and help with one: Check: A sound source emits sounds of frequency 210 Hz that travel through still air at 340 m/s. The source moves away from the stationary listener at 80 m/s. Find the wavelength of the sound waves...
  44. S

    M Underwater Vehicle Water Pressure

    Find water pressure of 3218 meters underwater vehicle with a volume of 25 cubic meters. Am I on the right track with ans: 25*210e-6*3218
  45. M

    Solving Water Pressure Problem with 8" Pipe and 90 Degree Turn

    Hey guys, I've been reading threads on here for a little bit and now I have a question I need some help with. I tried doing a search, but I didn't really know what I was looking for so it wasn't too successful. But here it is: My boss gave me this question to figure out and I'm not really...
  46. G

    How can I do this?Calculating Torque on a Dam Gate Hinged at the Water Surface

    There is a gate in a dam. The upper edge of the gate runs along the water surface. The gate is 2 m high and 4 m wide and is hinged along a horizontal line through its center. I have to calculate the torque about the hinge arising from the force due to the water. I know how to calculate torque...
  47. M

    How would I calculate water pressure in a vertical column?

    How would I calculate water pressure in a vertical column? I had about a 17 foot PVC tube with a 4" diameter filled with water. What equations could I use?
  48. R

    Can you calculate water pressure with just flow rate and hose diameter?

    Given only the rate of flow in gpm and the inside diameter of a hose in inches, is it possible to calculate the pressure of water leaving the hose? I have no experience or training in this area but it seems to me that more information would be required. Any help will be greatly appreciated.
  49. Another God

    Water Pressure in Conical Tank Question

    I was wondering if anyon could help me out. You have a conical tank with a top diameter of 1m, going down to an outlet of 150mm diameter, height of the tank = 3m, and it's full of water. Assuming an air pressure of 15psi, what is the pressure at the 150mm opening? (the bottom)? Does the...
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