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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.

584 questions with no upvoted or accepted answers
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6
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72 views

Temperature-pressure plot for superconducting records?

Eremets et al. (arXiv:1812.01561, Nature 569, 528–531 (2019)) and Hemley et al. (arXiv1808.07695, PRL 122, 027001 (2019)) have reported new high-temperature record for superconductivity, as covered by ...
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91 views

What will the excess pressure of a water drop on a table be?

I'm aware of the formula for excess pressure of a spherical drop given by :$$\frac{2S}{R}$$ Where $R$ is the radius of the drop. But what if the drop was on the floor? Using the formula for excess ...
5
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1answer
66 views

Pressure underneath wave

I enjoy water sports and activities in the water. I've swam around and dived down enough to need to equalize my ears and in general have felt water pressure. I've since taken up surfing and have ...
5
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2answers
260 views

How to calculate pressure exerted by a rocket's exhaust on a surface from a certain altitude?

How do you calculate the pressure that is exerted on a surface (say from a rocket engine) at an arbitrary altitude? For example, pretend I know the exit velocity and pressure of a rocket engine at an ...
5
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2answers
3k views

Inverted U manometer

I have some doubts on inverted U manometer. In the picture there is one U inverted manometer, the space above the liquid in the manometer is filled with air which can be admitted or expelled through ...
5
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1k views

Does the "luk" space suit in Seveneves make sense?

Tiny spoiler of the book Seveneves ahead. Early in the book, the Russian space agency develops an onion-like space suit called the "luk" (the Russian word for onion). It works like this: A ...
5
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1answer
52 views

Is there a material with non-monotone density dependence on pressure?

Is there a material with such non-linear effects (including chemical reactions, phase transitions etc ...) so that there would be range where pressure increase would yield density decrease? What ...
4
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1answer
207 views

Flow through a hole in a sphere

I have a sphere of diameter $D$ (radius $R$) with a small hole of diameter $d$ (radius $a$) in it, with air flowing through the axis of the hole: I am trying to estimate the drag force due to ...
4
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2answers
119 views

Over how large an area does an airplane in flight increase the pressure on the ground underneath it?

A plane exerts downward force on the air, so the ground must exert greater upward force on the air while a plane is in flight than when it is not (in a steady state where the air has no net ...
3
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1answer
59 views

How to define energy density and pressure for a scalar condensate?

Consider a scalar field theory in flat spacetime whose Lagrangian reads $$\mathcal{L}=\frac{1}{2}\eta^{\mu\nu}(\partial_\mu\varphi)\partial_\nu\varphi-V(\varphi).$$ Then the energy-momentum tensor ...
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0answers
35 views

How do we know sound pressure squared is proportional to the power in the sound wave?

I am trying to find the equation that explains why we can say the pressure exerted by a wave (squared) is proportional to the power. I see this claim made a lot but I can't tell where it comes from.
3
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4answers
99 views

If liquid water is constrained in vessel then the temperature is dropped below freezing will ice form?

If liquid water is constrained in vessel then the temperature is dropped below freezing what pressure would be measured assuming the vessel is unbreakable? Or put another way, will ice form if the ...
3
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0answers
169 views

Is there any use of a quadratic equation of state in FLRW cosmology?

Consider standard FLRW cosmology. Usually, the relation between energy density $\rho$ and pressure $p$ of a cosmological fluid component is linear: \begin{equation}\tag{1} p = w \, \rho, \end{...
3
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1answer
971 views

What is the most efficient way to pour a liquid through a funnel?

Be it in cooking or an experiment, when transferring liquid from one container to another using a funnel should you: (a) pour it all straight into the funnel, filling it up and waiting for the liquid ...
3
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0answers
179 views

Derive mechanical pressure from strain energy density

Similarly to thermodynamic pressure, when we have: $$P_{therm} = (\frac{\partial U}{\partial V})_{S}$$ Can we define the mechanical pressure for a fluid as: $$P_{mech} = \frac{\partial \psi}{\...
3
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0answers
391 views

What is the Planck Pressure?

What exactly is the Planck Pressure? According to wikipedia the Planck pressure "is not found except for shortly after the big bang or in a black hole". But wouldn't the pressure inside a black hole ...
3
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0answers
82 views

Behaviour of Altimeter at different temperatures

I have realized that the Altimeter of my bike computer (it uses Air Pressure to determine altitude and needs to be calibrated every start) is not consistent at different temperatures. At the Start ...
3
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0answers
366 views

Amount of Breathable Air in a Depressurized Scuba Tank

The question: How long could a person survive in an airless chamber using only the oxygen released from a 100ft^3 tank containing 32% oxygen? Long version: I'm doing a story on a man who allegedly ...
3
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0answers
362 views

Pressure inside a typical white dwarf

Does any one know the order of magnitude of pressure inside a typical white dwarf (better with reference)? Thanks! I think it should be $m_e^4c^5/h^3$ (may be multiplied by $\pi$), which is $10^{22} \...
3
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2answers
766 views

Are low pressure and high pressure areas responsible for rain?

My understanding is that low pressure areas are susceptible to rain. However, high pressure areas have no rain. Now, I want to correlate this with the following areas - Lower Hutt, Wellington , NZ - ...
3
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0answers
937 views

Suction from flowing water

My memory from physics says yes but I want to check. Our pool is dirty and our vacuum is broken. If I were to stick the vacuum hose into the pool drain, would the flow of water going into the drain ...
3
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0answers
517 views

Superconductivity: how does the critical temperature depend on the pressure?

This question is inspired by a recent publication, in which researchers managed to boost the record critical temperature at which a substance becomes superconducting by applying an enormous pressure ...
3
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1answer
581 views

How to get the pressure amplitude at any spatial point?

Working on the pressure equation from the linearized euler equations, I stumble across a very simple problem : How, from the pressure solution of the specific equation (see http://www.acs.psu.edu/...
3
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0answers
974 views

How would water drain out of a sealed pipe?

While hiking through the Grand Canyon, I started wondering. Say we have a pipe for the purpose of transporting water across a canyon, with the bottom submerged in a pool of water. Like the blue line ...
3
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0answers
4k views

Trouble justifying calculation of force on a sphere due to radiation pressure

I am attempting to calculate the force on a sphere in a plane wave of light where the light has intensity $I$. My calculations have concluded that, regardless of whether or not the sphere absorbs or ...
3
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3answers
158 views

Concept regarding Ventury Tube-Bernoulli application

I was recently studying applications of Bernoulli Equation and came across the Ventury tube. This is diagram I have used to analyse the venturimeter. I understand how we obtain the first equation ...
3
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5answers
983 views

How does the vertical distance beneath the surface of a fluid create pressure? (thought problem)

Specifically, I am trying to wrap my head around this scenario but can't do so solely by thinking about the weight of the fluid. Imagine a perfectly still lake. If you dive into the lake, the ...
3
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1answer
741 views

Explaining the shape of a raindrop and a drop of mercury

I saw on wikipedia that the shape of a raindrop is explained by using Laplace pressure. But why? Since the drop is in motion, we shouldn't be able to use an hydrostatic law, am I wrong? The ...
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0answers
34 views

Why does bringing a helium filled latex balloon close to my ear make it feel pressurized?

Title pretty much says it all. Got my son some balloons for his 1st birthday. He was playing with them while I was holding him and everytime he brought one closed to my ear it made my ear feel ...
2
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1answer
49 views

Deformation of a sphere

I am currently building a computational model for a simulation of a rover landing on the surface of mars. As part of the assignment I need to model airbags being used to cushion the fall. (Assuming ...
2
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0answers
37 views

Coffee quality and temperature

The question is about adjusting the size of particles of coffee powder to temperature. It is said that properly grinding the coffee grains is cricual for making good coffee (I have an espresso ...
2
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2answers
54 views

Saturation vapour pressure and the effect of ambient gas other than water vapour

Water (or any liquid/solid for that matter) has a saturation vapour pressure (SVP) that follows the curve given by Clausius-Clapeyron. At room temperature the SVP of water is about $0.023$ bar, so in ...
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0answers
30 views

Water flow through a ventilated orifice

Before I begin, please excuse the rushed and poor schematic made in haste. I am not very knowledgeable in fluid dynamics and was curious when I observed the scenario below. A water droplet of mass M ...
2
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0answers
58 views

What is the physics behind why incorrect cuff size for measuring blood pressure manually or automatically lead to inaccurate results?

The biophysics behind measuring systolic and diastolic blood pressure manually with a cuff and stethoscope is that Determine the approximate pressure it takes for the cuff to occlude the brachial ...
2
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1answer
72 views

How does air flow within a melodica when two key are pressed?

I'm trying to understand the air flow within a melodica. A melodica is a wind instrument that has a piano-like keyboard. Pressing on a key opens an airway so that air entering the melodica's air ...
2
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1answer
83 views

Can I use Pascal's principle to destroy any airtight container?

I am looking at the following textbook problem (please note that I am not asking for a solution to the problem, only using it as a motivating example): A host pours the remnants of several bottles of ...
2
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2answers
60 views

Can we have pressure with zero net force on a 2-d plane

From Wikipedia: Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Suppose we apply 2 equal and opposite forces on a 2d ...
2
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0answers
53 views

Confused about summing over the velocity squared term

Consider a cubical box, L on each side. The box contains N molecules of ideal gas, each of mass m. All collisions are elastic. The force exerted by one molecule when it collides with a wall of ...
2
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0answers
94 views

Does tilting a liquid develop shear stress on its surfaces?

Please help me these confusions I have. If I tilt a cuboidal container containing an ideal fluid (non viscous liquid), does a shear stress develop on the liquid due to some shearing force acting ...
2
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0answers
143 views

Integrating to find net pressure and force on a sphere by a fluid

How would I go about solving for the net force on a sphere exerted by air pressure as a result of pressure being dependent only on the vertical position of the ball? When the sphere it is placed in a ...
2
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1answer
179 views

How to calculate acoustic impedance of a megaphone?

I'm working on a physics problem that asks how a passive megaphone (simple cone shape) can optimise the transfer of the human voice, compared to not using one at all. I understand that some of this is ...
2
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0answers
126 views

Why did this bottle crumple?

These two empty 2-liter soda bottles were left forgotten in the back of a closet for three years. When they went in, they were both in good shape. They were both resting on top of something, with ...
2
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0answers
336 views

Estimating the Pressure of Earth's Center

The pressure of a medium of density $\rho$ and in a graviational field with strength $g$ at a depth of $z+dz$ is equal to the pressure at $z$ plus the pressure caused by the weight of a slab of volume ...
2
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2answers
406 views

Why does air get trapped below water pouring into a glass?

The drinking-water-tap at my workplace has a low pressure continuous stream of water. When I pour water into a glass which has at least about (depth) 5cm of water in it, surprisingly large air bubbles ...
2
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0answers
63 views

What is the equation of state of foam, on a macroscopic scale?

Consider a large amount of soap foam (or any other substance producing foam), of mass density $\rho$ in a gravityless environment. What is the internal pressure $p$ of that foam, viewed as a fluid on ...
2
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0answers
70 views

Proof that pressure rises in a fixed control volume

I am looking for a proof using Bernoulli's equation that that for $Q=(Area)(Velocity)$, $Q_{in}>Q_{out} \Rightarrow P_{inside}>P_{outside}$. I read that for a computer, if the case fans blow a ...
2
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4answers
699 views

Can someone explain why there is water in this vacuum chamber?

I work at a water treatment plant that uses a vacuum system to pull the water into the filters and backwash the filters. In the middle of the vacuum system there is the vacuum chamber. What I don't ...
2
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0answers
74 views

Computing the velocity of fluid along the length of a cylinder

I am modelling the flow of fluid through a cylinder of length L.The cylinder is divided into three segments(each segment of length L/3), there are four nodes(i=0,1,2,3). I'm trying to compute the ...
2
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0answers
66 views

How to model pressure loss over time for air in a cylinder with a hole

Related to an engineering project I will be working on. The situation is that essentially I will have a closed cylinder with a small hole on the side, which allows the air inside to be at equilibrium ...
2
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0answers
142 views

Can a scalar field also has positive or zero pressure?

In inflation theory, the inflaton field produce negative pressure to drive inflation. But now I’m going to ask about scalar fields in general, not the inflaton field. Can a scalar field also has ...

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