Questions tagged [pressure]

This tag is for questions relating to pressure, in the physical sciences, the perpendicular force per unit area, or the stress at a point within a confined fluid.

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How high pressure, high temperature liquid refrigerant exiting a Thermostatic Expansion Valve (TXV) turns into low pressure, low temperature liquid?

In a refrigerator or heat pump, how does high pressure, high temperature liquid refrigerant exiting a Thermostatic Expansion Valve (TXV) turn into low pressure, low temperature liquid? Is this a ...
Geremia's user avatar
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Integration of Pressure across Nozzle

[] 2Now, I have encountered a problem, I need to calculate the net Force in the $x$-direction. I want to calculate it through integrating the pressure field inside the nozzle. Assuming the exit of the ...
mohamed tamer's user avatar
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On hydrostatic pressure and weight

I'm doing some thought experiments about hydrostatic pressure and weighing setups on scales. This really confused me, so I really want to pick your brain about this and get some clarity. Consider the ...
Mathematician 42's user avatar
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Thermodynamic pressure in liquids

In equilibrium and from the theory of classical thermodynamics, we must have that the pressure in a system is constant throughout. Consider a system like liquid in a test tube. We know from fluid ...
EE18's user avatar
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Increase water pressure (e.g. for watering the garden) using the principle of a hydraulic press

Does anyone know a device that incorporates this principle? Process is as follows: You get a lot of water at low to mid pressure (let's say 1 bar) A device D converts the work that 1 liter of water ...
zonksoft's user avatar
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Where does the centripetal come from, in a cyclone?

It needs a tremendous amount of impulse ($Force\times time$) to keep the large mass of air and water vapor spinning for several days. Where does the sustained force come from? The centripetal force in ...
paki eng's user avatar
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What is happening to the air pressure in an extremely high-intensity low-frequency sound wave e.g. 30 Hz at 100 dB?

I'm doing research on low-frequency sound in music and one text states 'High-sound pressure levels condense air – noticeably thickening it, making it feel heavier.' Is this true and what does that ...
Spectre's user avatar
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Why $p= -\frac{\partial U}{\partial V}$?

In Callen's book, in page35 he defined $$p= -\frac{\partial U}{\partial V}$$ where does it come from? I thought it might come from a reversible process where $ dU=dQ+dW=TdS-PdV$(If the amount of ...
Raffaella's user avatar
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What does the $p$ in the formular $dU=Tds-pdV$ refer to?

In Callen's book (Thermodynamics and an I, second edition)p36 2.6 Based on what he said above, it seems like $p$ is the intensity of pressure inside the system. but when I asked my friend, he said the ...
Raffaella's user avatar
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Does physical equilibrium occur at specific temperature and pressure?

Does physical equilibrium occur at only specific temperature and pressure? Like does equilibrium occur only at $ 1 atm $ and $0⁰C$ between water and ice? If I change temperature or pressure will the ...
O Ji's user avatar
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Will just the increase in height of water column increase pressure or does mass play any role in it?

As we know pressure exerted by any liquid at any given point in a container can be calculated by the formula $P = \rho g h$. Product of density of fluid, acceleration due to gravity and the depth from ...
Princeley D'mello's user avatar
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Why is $\bar{h}$ halfway from the surface instead of being the same height as the resultant force $(2/3) h$?

I'm confused with the formula for hydrostatic force $F = yhA$. The force follows a triangular load where the resultant force is at 2/3 of the height, but $h$ in the formula doesn't follow this height. ...
jaquantavion's user avatar
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Understanding the slanted manometer - what happens to the tube normal force?

Vertical manometer Consider a manometer filled with water. Given a pressure $p_0$ at height $y=h$, The formula for the pressure $p$ at $y=0$ is $$ p = p_0+\rho g h $$ One way to derive this is to ...
nwsteg's user avatar
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How was the Titan submersible implosion time calculated?

Many experts commented about the Titan submersible that the implosion took few milliseconds. What is that assertion based on? What physics computations lead to that time? I had imagined an abstract ...
quinzio's user avatar
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Pressure affecting temperature in between layers

Precured Tread rubber is mounted over a tyre which is buffed and coated with vulcanizing solvent and bonding gum. The curing process is done in an electric heating chamber. The tyre is inflated upto $...
Renwick Pereira's user avatar
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Calculate Change in Tank PSI per breath at depth

I am a scuba diver, trying to understand some physics that occurs throughout a dive. Primarily I am trying to understand the surface air consumption (SAC) derivation. For those unfamiliar, SAC is the ...
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Change in temperature between pressed objects [closed]

Will there be a change in temperature at the surface of contact between two bodies if they are pressed against each another with a pressure of 50psi for a period of 12 hours? If yes then how much ...
Renwick Pereira's user avatar
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Questions about dark energy and negative pressure

The existence of dark energy leads negative pressure. Is the pressure can be anisotropic? What situation can cause anisotropy of pressure? Further, Is the pressure can be negative in some directions ...
Dongba's user avatar
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Does pressure in a closed container increase or decrease with increase in acceleration of the container?

Let there be some air contained in a vessel whose walls are elastic. The vessel is closed and we impart some velocity to it. Please note that the gas inside the container is stationary w.r.t. the ...
user146290's user avatar
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Behavior of air in a submersible implosion

I hope that this community could help to clarify some unproven but widespread claims regarding the implosion of the Titan submersible. Background: The 2023 Titan submersible incident created a wide ...
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How does the hydrostatic paradox operate when a column of lighter liquid rests atop a “floor” of heavier liquid?

I know that, according to the hydrostatic paradox, the height of a homogeneous liquid is the only determinant of pressure within that homogeneous liquid, and the shape of its container does not affect ...
Russell's user avatar
5 votes
2 answers
250 views

Help me understand extreme pressure

So we have the tragedy of the submersible being lost near the Titanic site. I am trying to understand the pressure the vessel was under. I have heard the "$1$ atmosphere for every $10$ meters&...
Tony Ennis's user avatar
4 votes
2 answers
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Why chemists usually only deal with enthalpy and not internal energy? [duplicate]

From what I understand, enthalpy only seems like a mathematical intermediate step. Why do we have a special name for it?
Angry Granny's user avatar
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Is the work done by the atmospheric pressure negligible? [closed]

In the problem there is a cylinder with a massless and frictionless piston, initially at rest. A weight is placed on the piston and the gas undergoes an adiabatic compression. The problem specifies ...
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Sideways forces on submerged masses

Imagine 2 submerged masses in a liquid that are free to move and in close proximity. Pressure is exerted on all surfaces. Will the sideways pressure force them together? There will be equal and ...
Billo's user avatar
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-1 votes
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Why is it easier to fill a chilled metal cylinder with gases? [closed]

Where I work, we chill life raft inflation cylinders before filling then with CO2, N2, and inert gases because we heard they fill easier and quicker if chilled first. Is this true?
Judy Swanson Muddy Mermaid's user avatar
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2 answers
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What path will air take to leave the space station?

Hi everyone, lets say we have a circle shaped space station and there was an accident where we got a hole (hole A on the picture) on a station and now most of the station is vacuum except for one ...
Exe's user avatar
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Contradiction of Bulk's Modulus and Pressure exerted by a static liquid

My question is about a scenario where a certain amount of air is passed through water. Now, this air will form a bubble and due to the buoyant force acting on it, it will rise. We know that the ...
RON's user avatar
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-2 votes
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Why is pressure not a vector quantity? [duplicate]

A vector quantity has magnitude and direction. Pressure is force applied per area. Wouldn't that be the force having a direction towards the area? And 'as Newton came to realize, within the body of a ...
Sturburn's user avatar
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Can anyone explain how high atmospheric pressure affects fishing when water cant be compressed?

So, I am both a qualified scuba diver, and a fisherman. I understand that for every (approximate!) 10m you go down under water, you add an atmosphere of pressure, and things get squeezed. Conversely, ...
Karl's user avatar
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Bernoulli equation and wind

Bernoulli equation is often used to explain how rooftops are blown off during tornados: the usual explanation is that the high speed of the wind il related to a lower pressure outside the house, ...
Dario's user avatar
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1 answer
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I can't fill butane gas in a torch lighter at 3500 meters

I'm currently on a very high place, about 3,500 meters above sea level. I'm trying to fill up a torch ligher with a butan refill canister, but the torch doesn't filled up. When at ~sea level altitude, ...
Garcia's user avatar
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2 votes
3 answers
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Dependence on $(p,V,T)$ rather confusing

I am currently taking the freshman thermodynamics course and have asked several times for explanations of the relationships which can, and which cannot, and why they cannot. But I still don't really ...
Masterrun80's user avatar
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Isotropy of fluids vs. hydrostatic pressure (conflicting concepts to me)

The formula for absolute hydrostatic pressure on Earth is $$ p = ρgh + p_{atm}, $$ where $ρ$ is the density of the liquid, $g$ is the gravitational acceleration, $h$ is the depth of the liquid, and $...
Edward Chen's user avatar
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0 answers
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How to optimize the air pressure produced by a black pipe in the sun? [closed]

So, I'm thinking of ways of overdoing the passive aeration of my compost bin. Basic setup is a (60L) bin with a pipe with holes through the middle; air is supposed to flow into the pipe and its holes ...
Giogina's user avatar
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1 answer
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Question in High pressure high boiling point

I'm Finding it hard to visualize how higher pressure makes the boiling point higher. I understand how pressure increases then temperature increases such that say air molecules compressed gives it ...
Naveen V's user avatar
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Relation between the coefficients of Virial expansion and fugacity expansion?

One can write pressure of an interacting dilute gas as an expansion in its fugacity $\xi = e^{\beta \mu}$ as, $$\frac{P}{n_0T} = \sum_{l =1}^\infty b_{l} \xi^{l}$$ From this we can calculate the ...
Bimaphys's user avatar
2 votes
1 answer
94 views

Internal pressure in rigid gasoline tank from increase in temperature [closed]

I was hoping to find a chart (or detailed table) that depicts the increase in internal pressure for a rigid tank full of gasoline from increases in temperature. If this is not available then I wanted ...
ChartProblems's user avatar
4 votes
2 answers
266 views

What is pressure energy in a closed system?

Let's consider a gas inside a closed cylinder with a piston. This can be considered a closed system. The First Law of Thermodynamics (FLD) for a closed stationary system can be given as Q = U + W ...
GRANZER's user avatar
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UHV chamber starts oscillating once the pressure gets down to $2.5 \times 10^{-5}$, Why?

Using a new Edwards nXDS15iC scroll pump as a roughing pump for a new Kurt Lesker EMT3304 turbo pump. Chamber is a cylinder about $100{\textrm{ ft}^3}$. We have identified leaks and corrected using a ...
Michael Buchanan's user avatar
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3 answers
138 views

How can centerline stagnation streamlines exist?

A stagnation streamline is a streamline that ends on the surface of an object, resulting in a stagnation point. Consider now the stagnation streamline for a symmetric object, which is along the ...
Thomas Wagenaar's user avatar
1 vote
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Creating vacuum in a rubber hose by replacing air with helium which escapes through osmosis?

Yesterday I heard this: suppose you have a rubber hose, in which you inject helium, which replaces the air which was there before. Now, because there is no helium in air, so the partial pressure is ...
wondering's user avatar
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Mass density of radiation in Friedmann equation?

$$\frac{{\ddot a}}{a} = - \frac{{4\pi G}}{3}(\rho + 3P) + \frac{\Lambda }{3}$$ In the case of matter, pressure $P=0$, In the case of radiation, pressure $P=(1/3)ρ$, In the case of cosmological ...
D will's user avatar
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1 vote
2 answers
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Why does the volume of a liquid seem to increase and then rise when you release pressure too fast in a car's cooling system?

So I was pressure testing the cooling system of my car with a kit where you fix a cap, a gauge and a hand pump to the expansion tank and then pressurize the system to 1.5 bars (mostly European cars go ...
Reg's user avatar
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10 votes
2 answers
3k views

Reverse blood flow in an IV

When the IV drip for a patient is completed, the patient's blood will flow back. This is apparently due to the pressure difference. However, IV needles are inserted into veins in the direction of ...
Starlight's user avatar
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0 votes
2 answers
96 views

Could Dark Matter have negative pressure?

Is it possible for dark matter to have negative (but negligible) pressure? How small should it be to fit with observations? Dark matter pressure is actually known and measured?
Antoniou's user avatar
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2 answers
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Why doesn't water inside a glass enter a straw when you close the top of the straw before putting it inside the glass?

Why doesn't water inside a glass enter a straw when you close the top of the straw before putting it inside the glass. Shouldn't the atmospheric and pressure of water push the water into the straw ...
abbas azani's user avatar
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1 answer
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What is the physical meaning of the pressure of an acoustic point source being complex?

Context From various sources of Acoustics (such as "Acoustics - An Introduction to Its Physical Principles and Applications" by Allan D. Pierce and "Fundamentals of General Linear ...
ZaellixA's user avatar
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How to understand this derivation of Raoult's Law?

A derivation of Raoult's Law in a textbook is as follows: I cannot follow the chain of arguments: Why should $p_{A0}=p_{B0}$ ? A and B are basically two different substances, each of which has a ...
MichaelW's user avatar
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2 votes
1 answer
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Osmotic pressure "equilibrium"?

Consider a box with two compartments separated by a semipermeable membrane. The first compartment is initially at pressure $P_0$ and contains the solvent ; the second compartment is initially at ...
lohey's user avatar
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