# 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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### 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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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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 ...
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### 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 ...
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### 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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### 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.
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### 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 ...
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### 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{...
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### 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 ...
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}{\...
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### 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 ...
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### 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 ...
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### 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 ...
362 views

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### 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 ...
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### 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 ...