Pressure Definition and 999 Threads

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. ib43

    Thermal physics problem -- Pressure and temperature of air in a refrigerator

    There is this one problem from past exam papers which I cannot seem to do: The air in a kitchen has pressure 1.0 x 10^5 Pa and temperature 22'C. A refrigerator of internal volume 0.36 m^3 is installed in the kitchen. (a) With the door open the air in the refrigerator is initially at the same...
  2. C

    Maintaining higher air pressure in an "open" leaky container

    Hey all, I've got a container that needs to maintain a certain amount of air pressure for the contents inside to develop correctly. However, it is an open container (like a big box with a hole in it), so without a pump constantly pushing air into it, it will rapidly drop pressure to equalize...
  3. T

    Is cavitation worse at depth? (Fluid pressure and Vapor pressure boiling)

    I am wondering about the impact of the hydro static pressure of a fluid on its boiling point. The simplest real world example scenario I can think of is the rate/onset of cavitation at a large depth vs a shallow depth. As we increase the submarine propellor speed to a speed where the adjacent...
  4. R

    Could pressure washers solve the Australia bushfires problem?

    The JetLev water pack puts out about 60 psi but can lift a 400 pound weight 30 feet in the air. A lot of water can be provided by just those water jet pack units, 1,000 gallons per minute, providing 400 pounds of force, all of that powered by a 200 hp pump that trails behind remaining in the...
  5. bigyabbie

    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...
  6. vxiaoyu18

    Keep working on the liquid pressure problem

    Without calculating the friction, if the force of gravity on the piston, the initial force F on the piston S is what? 1. F=-ρgSH; 2. F=-（1/2）ρgSH; 3. F=0; 4. Other. I'm not sure which is the correct result, can someone help me analyze it again?
  7. Ayrflyer

    Need help trying to mimic a phenomenon associated with air pressure

    Good day everyone, Hope all is well. Bare with me as I am beginner in the field of understanding air pressure. But could really use help with a certain phenomena that I have been observing with an experiment I have had success with. I am then attempting to build an apparatus that mimics its...
  8. D

    Accounting for Liquid Water Density in Ideal Gas Pressure Calculations

    First calculate the total pressure, but that gives me p2=p1*t2/t1 = 2,86 bar and partial pressure of 0,87 bar which is wrong. any tips?
  9. B

    Density of air at one atmosphere pressure

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  10. T

    Calculating the Pressure at a Reservoir

    Summary:: Calculating the Pressure at a Reservoir Hello all I am struggling to calculate the pressure at a given point, i am getting all sort of strange answers and i was hoping someone could help. The question is as follows:- From this i have tried to draw a sketch of the problem (not...
  11. T

    What is Pressure Energy & How to Calculate it?

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  12. Vivek98phyboy

    Excess pressure inside a Liquid drop

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  13. Uchida

    Does radiation pressure depend on the wave phase?

    Hello to all, Does radiation pressure depends on the wave phase of the electromagnetic wave hitting a surface? Or, can the radiation pressure be modeled as a sin/cos wave function, where force due to radiation pressure F = P/c would be the average over one cycle? (P = power, c = light speed...
  14. T

    Difference between Absolute and Gauge Pressure

    Hello all I was wondering someone could help clear up my understanding about the difference between Absolute and Gauge Pressure. After some reading i have been told that the Absolute Pressure is pressure taken at 0 relative to a vacuum. I am trying to understand what this actually means...
  15. carveranderson

    Pressure vessel made with a metal tube and a clear polycarbonate lid

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  16. T

    Impact of Atmospheric Pressure on the Water in a Tank and a Pipe

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  17. Aletag

    Work done BY the gas in a cyclic thermodynamic process

    Since the assignment asks the work done by the gas, that should be equal to P1*(V2-V1) aka the area under the P1 line. Do I have to subtract the work done to the system or is this the solution already? If so, why do I need P2?
  18. maxelcat

    Pressure of an ideal gas -- A Level Multiple Choice Problem

  19. D

    Isothermal process involving changes in Volume and Pressure

    P1 = 2 bar V1 = 5.1L P2= 1bar V2 = V1P1/P2 = 10,2L, so the volume of gas would double? or should the absolute pressure be taken into account P1= 2bar (3bar absolute), V1=5.1L P2= 1 bar V2 = 15,3L?
  20. X

    Measure flow rate with a manometer (pressure gauge)

    Hello! I have a volume of 50 liters which I pressurize with air so that I read 1 bar on the manometer. But there is a leakage in the volume so after 30 sec the manometer shows 0,5 bar. What is then the air flow ( liter / min) of the leakage?
  21. E

    Confused about use of external vs internal pressure in thermodynamics

    I've learned that ##W = -\int{P_{ext} dV}##, and only during a reversible/quasi-static process where ##P_{int} = P_{ext}## can we write the work done on the gas in terms of the internal pressure (and consequently use ##PV=nRT## etc. which apply to the internal gas). However, a lot of sources...
  22. A

    High pressure gas discharge fusion

    I thought to myself , have there any been any physical attempts or calculations in theory about the possibility of creating a net electrical gain of energy from a pulsed fusion approach where a high pressure/density gas mixture is prepared constantly within a container and a high current pulse...
  23. T

    Engineering Understanding Force / Pressure Equation

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  24. Emanuel Silva

    Pressure generated by a column of air

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  25. C

    Combine 3 Eqns for Plasma in a Solenoid

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  26. F

    Is Voltage a measurement of pressure?

    Summary: Volts When measuring an electrical currents voltage, are you actually measuring the pressure emitted in electricity
  27. T

    Repost/Merged Threads - Density: pressure and temperature dependency

    See image
  28. F

    What Happens When You Dive Too Deep?

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  29. TOMMiB

    The Pressure in Interstellar Space.

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  30. Kaushik

    Pressure on a sample of fluid (at rest)

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  31. B

    Can increasing the speed of light lead to more efficient photon rockets?

    Radiation pressure that light provides is weak. The photon rocket only gives thrust on par with rockets if you are willing to exhaust way more energy than normally used for rocketry (antimatter/matter annihilation). By that time your exhaust beam will be loaded with enough photons to nuke...
  32. F

    Why is static pressure called "static"?

    Hello, I am still perplexed on why the pressure term ##p## in Bernoulli and Euler equations is called "static", even if the fluid is flowing (moving). Are there historical or other specific reasons? In hydrostastics, the pressure at a certain depth is called hydrostatic which makes sense since...
  33. sebastian281172

    Pressure applied to the ground by a man standing on stilts

    Homework Statement: How much pressure is applied to the ground by a 52 kg man who is standing on square stilts that measure 0.06 m on each edge? Homework Equations: p=(F/A) P = (F/A) = (52*9.81)/(.06^2) = 207100
  34. WhiteWolf98

    Clausius-Clapeyron equation to estimate sublimation pressure of water

    Before this question, the questions were about the Clapeyron equation, and how to estimate ##\Delta s##. I'm completely put off by this question however, and don't know where to start. I've found that the triple point of water is at ##0.01°C##, and there is indeed data in the table for...
  35. John Archer

    Controlling (liquid) flow and pressure at very low flow rates

    System in question. Centrifugal pump (seal packing is water cooled) Fluid is water. Main system pressure is 55Psi. I need the water pressure to be around 25Psi. I also need the flow rate to be very low (think, maybe 1oz per minute). Basically, I need slightly more than say 30 drops per minute...
  36. F

    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...
  37. R

    Pressure drop due to holes in a pipeline?

    We have a project that relating with pipeline system and pressure control, the project is actually having goal to knowing how much pressure drop will occurs in pipe line system that in initial condition the pressure inside the pipeline staying at steady or constant in particular psi and at the...
  38. S

    Earth's Atmosphere -- Is gravity the reason we have air pressure?

    I have read an article in Quora, where a person says that "Gravity pulls the atmosphere towards itself and that's one of the reason why our Atmosphere is still this way" and also adds that, "gravity is the reason we have air pressure in the first place. Gravity pulls on the atmosphere...
  39. Frigus

    How can the pressure be more in liquid flowing with less speed?

    Before I have read Bernoulli's theorem I believed that pressure is more in liquid flowing with more speed but today I have read Bernoulli's theorem where this theorem says that the pressure is more in liquid flowing with lesser velocity please tell me how can this explained,with equation I...
  40. EEristavi

    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...
  41. T

    Can a Y-joint at high flow velocity create negative pressure?

    Hello, I was wondering, for the understanding of my research, the following. I try to create a negative pressure using the venturi effect. There is a problem a.t.m. with the understanding (theoretical) of negative pressure. Let me qestion this: If i have a straight pipe. there is halfway in...
  42. falcon999

    Effect on air pressure and volume in an enclosed container

    Summary: I wish to understand if bubble formation in milk while being sloshed around, or the formation of separation layers will affect both the pressure and volume of the air head space above the milk Hi all : ) I have a basic physics question and sorry if its a very silly question: Let's...
  43. H

    Need stress value of aluminium for project work

    Summary: I am not a physics student but I really need to prove that aluminium will not deform 10m underwater Hi I am doing a project of a product which will sink underwater. It will be a sealed cylindrical vessel, length 2m, width 1m, thickness 0.02m. Aluminium 6061t will be used with a yield...
  44. Frigus

    What is pressure energy in Bernoulli's theorem?

    In Bernoulli's theorem I understood the gravitational potential and kinetic energy but I can't understand what is pressure energy.
  45. B

    Predicting flow rates of a pressure driven system

    Hi! I'm a student of pharmaceutical sciences which means that my physics knowledge isn’t that great ahah, if I say a big mistake in the following text, a thousand "sorrys" ahah: So, I am now writing my master thesis and currently I am finishing writing a part where fluid mechanics are...
  46. Frigus

    Why doesn't pressure depend on the shape of the container?

    As we know that liquids(same) at same height exert same pressure because of height difference but as I have a question in which there are some figures In which the (d) part lower part is extended horizontally,so by common sense the pressure in horizontal direction should increase But why at...
  47. Frigus

    Why do we feel pressure from the downside in a liquid

    We know that pressure at a point in liquid is due weight of water couloum above that point but why does we experience force from downside face of object
  48. AshPowers

    I Cosmological scale and the pressure of light....

    One of the things I have yet to come across in the explanation for the expansion of the universe is the effect of light... Most all of the matter we observe out there are stars - fusing nuclei and radiating EM energy in incomprehensible quantities... And this has been happening since the dawn...
  49. S

    Pressure of Slurry in a Stainless Steel Pipe

    I am trying to find the pressure in a ANSI stainless steel pipe with a nominal diameter of 10 in. A slurry of fiberglass and water is flowing through the pipe that has a viscosity of 3.2 centipoise. The flow rate through the pipe is approximately 3000 GPM. How can I figure out the pressure in...
  50. B

    Pressure Change: Understanding the Physics Behind Closing a Valve

    I was measuring the water pressure on my house using a pressure gauge with a hose bib fitting. So I screwed it on and the meter read 120psi. Then I started turning the valve off and the pressure decreased the more I closed the valve. There was no flow downstream of the valve (or anywhere...
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