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Questions tagged [pressure]

Force per unit area.

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1answer
34 views

Is it possible to drain all oceans' water to space? [duplicate]

Assuming: That I have an ideal straw (a very long pipe) from the ocean to space; That the straw (pipe) is ideal (will not break); That i can pump all the air from the pipe creating vacuum inside the ...
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1answer
30 views

Airflow due to differential pressure [on hold]

Is there air flow (low pressure) towards the cockpit of the interior of a pressurized aircraft due to the differential pressure between the cockpit exterior skin surface and the cockpit interior skin ...
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2answers
40 views

Deriving pressure from particle velocity: missing 1/3 factor

Let us assume we have a perfect gas, isotropic, homogeneous, inside a cube of side a. We want to calculate the pressure as a function of the velocities of the particles inside. We must find the ...
0
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0answers
12 views

How to measure wave vector from complex pressure?

I want to plot the dispersion relation in comsol for an acoustic waveguide. I am working in pressure acoustics, so my dependent variable is pressure. Comsol treats pressure as a complex number. How ...
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0answers
31 views

How to calculate air density on Mars based on specific pressure and Temperature? [on hold]

I am trying to solve a Physics question which includes air density of Mars and with my calculation, I'm finding value around $0.01045$: $$\rho_{\text{mars,air}}= \frac{P}{RT}= \frac{600}{287.05 \...
2
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1answer
41 views

When the barometer drops, my well level seems to rise - how?

I have a deep water well, with a length of 1/4" drip tubing, open at the bottom, taped to the pump 180' down. The other end of the tubing is connected to a gauge pressure sensor in the cabinet of my ...
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0answers
23 views

Determining pressure as a function of time for water filled balloon

Looking to determine pressure as a function of time for a water filled "balloon" at extremely high pressures (~90MPa) with a fixed flow rate out. This is to determine the time it takes to hit a ...
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2answers
52 views

Compression of gas [closed]

What happens when a gas kept in a metallic container is suddenly compressed via a piston and left for some time? Does the pressure increase or decrease?
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2answers
44 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 ...
3
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1answer
56 views

How does sharpening a pencil make it darker?

Why does a sharp pencil write better than a blunt one? Note that the force applied on each case is identical.
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0answers
24 views

How to generate force with air pressure [closed]

I am trying to figure out how to generate a substantial force for a short period of time by releasing pressure in a small high-pressure air tank. A rough estimate of the force required is 40 ...
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0answers
13 views

Compression to Maintain Temperature

Can a liquid in a pressurized container maintain a very cold temperature merely because it is unable to expand and become a gas?
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0answers
22 views

How do you reckon my mattress works? [closed]

So I have one of those "sleep number" mattresses, made by Select Comfort. Good mattress. It contains two air chambers, and has a pump which can inflate or deflate these air chambers to the desired ...
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0answers
13 views

Pressure on a Heat Exchanger in a piping system

I have a piping system that is supplied by a centrifugal pump. The system consists of pipe, 2 heat exchangers, some elevation gain and loss and ends up in an atmospheric tank. If I wanted to know ...
3
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0answers
98 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{...
2
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0answers
43 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 ...
0
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1answer
21 views

Water Hammer - Max Pressure Position

When using the Joukowsky equation: P=cpu To find a pressure rise in a pipe due to water hammer. How can I find the position along the pipe from the valve closure where the pressure rise is the ...
0
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1answer
13 views

Does changing the volume of Hg in the container of a Torricelli barometer affect the height of Hg in the tube?

When changing the volume of mercury in the container, its mass may increase or decrease, so the gravitational force acting on the inside bottom of the container may increase or decrease, and therefore ...
1
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2answers
34 views

Are forces of gases intensive or extensive?

What am I wrong at in here: I read that pressure is an intensive property. According to this and to $P=\frac{nRT}{V}$, can this be true: $(1)$: When $V$ is constant, increasing $n$ won't increase $P$,...
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1answer
24 views

Calculate change of pressure in a football due to insertion of a solid ball [closed]

Let's say I have a football of radius r1 inflated to pressure p1 and insert a solid metal ball of radius r2 (without losing any air), to give a new pressure of p2. Is there a formula I can use that ...
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2answers
45 views

Pressure being isotropic

We say pressure is isotropic. At any point in a fluid pressure acts equally in all directions, but pressure is perpendicular force per unit area so how can pressure be there in all directions as ...
0
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1answer
35 views

can generation of pressure create light?

If pressure is applied on a body , can mechanical stress produce light? , as electrons are produced in piezoelectricty. if yes , please answer or recommend any book/website/paper. Thank you
0
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1answer
55 views

Why did the liquid disappear from some unopened aluminum cans? My experience (read below) has not been answered [duplicate]

I’m posting my question because I read this original post. The post was from 2016, so I’m reposting in hopes that someone can answer. Here’s the original post: (Also, do not flag as duplicate. If you ...
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0answers
29 views

Hydrostatic pressure vs static pressure in a fluid

hydrostatic pressure is the scalar and isotropic pressure exerted by a fluid at rest at a certain point inside the fluid itself on the neighboring fluid parcels or on on an elementary differential ...
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0answers
24 views

Water vapor pressure in oxygen bubble

Suppose we have a source of O$_2$ bubble formation in water at specific nucleation sites, how can we estimate the water vapor pressure inside the O$_2$ bubbles? I know that: (1): $p_\mathrm{O_2}+p_\...
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1answer
36 views

Hydrostatic pressure: clarifications

Hydrostatic pressure is due to the weight of liquid. Do liquid molecules exert pressure on their neighbours molecules or only in objects that are in contact with them?
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1answer
31 views

Constant pressure

When we refer to constant pressure like in Charles law what is this pressure? The pressure of the gas or the pressure that the container (the piston maybe) exert on the gas? Also does atmospheric ...
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0answers
23 views

Stable bubbles in a vacuum

I want to make space bubbles that hold some gaseous stuff - at very low pressure - for a long time and through nothing but surface tension. I can't use soap water as the water will evaporate quickly. ...
0
votes
1answer
32 views

At what pressure do semiconductors break down? [closed]

So let's say you were going to send some electronics to the bottom of the ocean, 3-5km down. This would be about $5km*1000kg=5Mkgf/m^{2}$. So at what pressure do circuit boards, transistors, etc stop ...
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1answer
38 views

When a carbonated drink is opened, why does the liquid tend to flow out?

In other words, why does the coke flow out of it's bottle/can. Isnt the air trapped inside the container, so the air must flow out? What pushes the liquid to go outside the container? For example, we ...
3
votes
1answer
42 views

Why does the pressure change on uniformly mixing two liquids?

The two cylinders are connected the upper cylinder has a cross-section of A and the lower one has a cross-section of 2A (I've taken the cross-sections to be A and 2A as they are easier to work with ...
0
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1answer
48 views

Relative humidity, definition and its dependence on state variables

Relative humidity ($RH$) is defined by the following equation: $$ RH = \frac{p_{vap}}{p_{sat}} $$ Where $p_{vap}$ is the vapour pressure and $p_{sat}$ is the saturation vapour pressure. VAPOUR ...
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1answer
15 views

Why isn't the volume of the individual gas particles relevant to the total pressure in Dalton's Law of Partial Pressures?

I was reading about Dalton's Law of Partial Pressures in a textbook and the proposition is that under ideal conditions, the relevant factors are the pressures of the individual gases and their number ...
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1answer
32 views

PV diagram of pure substance

Why does the specific volume of saturated solid state of water decreases with increasing pressure and the specific volume of saturated liquid wrt vaporisation increases with pressure? Can anyone ...
0
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1answer
23 views

What would be the total pressure in this container in accordance to the Ideal Gas Law?

If I had an apparatus such as the one below: where each of the four blue lines represents a valve, and then I was to open the three lower valves such that the pipes connecting the three containers ...
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0answers
60 views

Demonstration of magnetic field lines “tension” and “pressure” using the Maxwell stress tensor

I would like to show that the magnetic fields lines are under "tension" along the lines and exert "pressure" perpendicularly to the lines, using the Maxwell tensor only. I have a sign ambiguity. In ...
14
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6answers
3k views

How is pressure an intensive property?

I've seen this question asked before but I can't find an answer to the specific point I'm troubled with. From the kinetic theory of gases, pressure results from molecules colliding with the walls of a ...
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0answers
37 views

Why are diamonds formed under high pressure? (use entropy)

My book asks how can diamond ever be more stable than graphite, when it has less entropy. I have to explain how at high pressures the conversion of graphite to diamond can increase the total entropy ...
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0answers
22 views

Do the height of the water columns decrease when we push pistons with constant speeds in this venturi pipe?

Let say when the pistons are kept stationary the height of the water columns are h. And we start exerting extra force on the left piston in figure, and the pistons are moving with constant speeds. ...
2
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0answers
51 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 ...
36
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8answers
6k views

Can a battleship float in a tiny amount of water? [duplicate]

Given a battleship, suppose we construct a tub with exactly the same shape as the hull of the battleship, but 3 cm larger. We fill the tub with just enough water to equal the volume of space between ...
0
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2answers
33 views

What happens to the pressure time graph when two musical instruments play at the same time?

I'm learning acoustics for the first time and I'm having trouble picturing what the pressure time graph would look like when two instruments play together. https://newt.phys.unsw.edu.au/music/flute/...
1
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1answer
21 views

Increase Air Speed at outlet

I have a set up that inflates a rubber jacket in order release the metallic rings from underneath it. I am currently having issues with not having enough pressure (force) at the outlet to inflate the ...
0
votes
1answer
67 views

Could a sufficiently massive Dyson Sphere under very specific conditions depend solely on electron degeneracy pressure for structural integrity?

Stuck in an argument. I claim this is theoretically possible: Provided you could build a type 1 Dyson Sphere, made from a supposed material that rivals the structural integrity of a white dwarf, i.e. ...
4
votes
1answer
104 views

How is pressure calculated in the early universe?

I'm trying to calculate the sound horizon from the start of time to decoupling. To do this I need to know the speed of sound and how it changes as the universe grows. The speed of sound in a fluid ...
0
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1answer
42 views

Limitations of converting pressure into kinetic energy

Bernoulli's principle states that an increase in the kinetic energy of a fluid occurs simultaneously with a decrease in pressure for isentropic processes. What then limits us from converting all of ...
3
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0answers
30 views

Temperature-pressure plot for superconducting records?

Eremets et al. (arXiv:1812.01561) and Hemley et al. (arXiv1808.07695) have reported new high-temperature record for superconductivity, as covered by MIT Tech Review and Physics Today. Not ...
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2answers
41 views

Microscopic idea of sudden extreme pressure difference

I'm having some issues understanding what's happening microscopic when there's sudden changes in the pressure. The microscopic idea, is that particles randomly bounces around each other. It's even ...
0
votes
1answer
32 views

Does increasing the stroke of a pneumatic cylinder create a need for a thicker wall?

So say you have a pneumatic cylinder (ram) with a certain length and wall thickness. The ram is pressurized to the same pressure each time (1000psi) Force is equal to pressure x area. So as the ...
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1answer
97 views

How can the Friedman Equation produce negative pressure or density?

As I understand it, the Friendman Equation provides the driving mechanism for Inflation.$$\frac{\ddot a}{a}=-\frac{4\pi G}{3}\left(\rho+\frac{3p}{c^2}\right)$$If $\rho$ or p is negative enough, you ...