Force per unit area.

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2
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2answers
143 views

How does force transmit through a solid block?

If you take a solid block, say, a cube of side length $l$ with density $\rho$, you place it upon a solid floor, and you apply an external pressure of $p(x,y)$ on the upper face ($x$ and $y$ define a ...
2
votes
2answers
72 views

Any general method of determining changes in speed of sound with pressure?

I need to correct speed of sound measurements in various gases for changes in ambient pressure, typically 700-1100 mBar. Is there any general theoretical model available for this? Especially something ...
1
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1answer
241 views

Equation involving; elastic modulus, poisson ratio, radius and pressure of a sphere [closed]

I am trying to determine the expansion of a spherical pressure vessel. I am certain that an equation exist that will define the change of radius of the sphere as the pressure increases. The vessel ...
-3
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1answer
72 views

Explanation of relationship between pressure and poiling point of water [closed]

Explain how an increase in pressure elevates the boiling point of water, while reducing the pressure depresses the boiling point?
0
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1answer
20 views

What are pressure threshold patches called in professional terminology?

I am making a small combustion chamber, and need to measure the pressure when a combustion occurs. This is a hobby project, so I don't have enough money to buy a dP cell with a remote membrane for ...
1
vote
1answer
43 views

Partial pressures - beyond the concept of point masses

Imagine that I have 100 atoms of oxygen and 100 atoms of lead put together in a container. By kinetic theory of gases, they should be considered as point masses thus the partial pressure of oxygen ...
0
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1answer
159 views

How to find the force due to fluid pressure over a surface?

The question is about sphere like surfaces, like the hemispherical base of a cylinder as shown. The cylinder is filled with fluid till the given height $h$, and the density of the fluid is $\rho$ ...
1
vote
2answers
185 views

Negative pressure

How is negative pressure created in a fluid system?Isn't it counter intuitive that we are reducing the pressure of a system containing no molecules(zero pressure) to a lower value?
0
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0answers
234 views

Self-made air pump - What does it take to pump up a balloon?

We are building a simple altitude-controlled balloon (idea borrowed from Google Loons). As part of that, we need an air pump to inflate a balloon acting as ballast (which is called a Ballonet in ...
0
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0answers
46 views

How much does barometric pressure change over minutes?

I have to correct an ongoing experiment for atmospheric pressure. This means that during the experiment I must read a chip that measures barometric pressure. The question becomes one of how rapidly I ...
2
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1answer
136 views

Can sound frequency create more ideal conditions for fire?

You may have seen the recent story of a device that engineers claim can extinguish flames using sound frequency. An older article loosely explains the theory behind how this works: Sound travels ...
1
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2answers
130 views

Air leaking out of a tire

My bike was not used for over 7 months, It has no holes on it. Yet I found it empty, is there a specific reason why air leaks out of objects without any "force" acting upon the tire to force the air ...
0
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0answers
57 views

Altitude altimeter application

What is the most precise formula to calculate altitude and what parameters should i considet such as pressure, temperature, dew point, ... I am developing an altimeter app and i don't know what the ...
1
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1answer
257 views

Difference between hydrostatic and uniaxial pressure

I'm confused with these two terminologies. Does 'hydrostatic' means every direction while 'uniaxial' means one direction? What're they usually used for?
0
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1answer
3k views

When to use h = Cp∆T or u = Cv∆T

I'm getting myself confused on when to use h = cp∆T or u = cv∆T where cp is the specific ...
1
vote
4answers
475 views

Can I blow soap bubbles (of air) inside a vacuum chamber?

When I blow soap bubbles from a liquid dish soap mixed with distilled water at atmospheric pressure at ground level both internal and external air pressure nullify and the tension of the bubbles holds,...
2
votes
1answer
198 views

How does water pressure manifest itself on the molecular level?

Second, related question: does water density relate to, or cause, water pressure? Everyone I talk to dismisses the idea that water density substantially affects pressure, and emphasizes that water is ...
5
votes
3answers
3k views

What if you opened a door in a spaceship without a spacesuit?

In movies/cartoons you see astronauts and people in spaceships opening doors and closing them again with no suits on. Is it possible in "real life" or would you die immediately? Because consider this: ...
1
vote
2answers
165 views

Microscopic definition of dynamic pressure of fluids

So we have a moving fluid and we know from Bernouli's equation that there is a term called dynamic pressure(not to be confused with the hydrostatic pressure of the fluid). So,what exactly is it and ...
1
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0answers
22 views

Practical nozzle question / mass of finger?

A spray bottle i own broke off its compressor tip so i fashioned another one from a rubber tube, a pen lid, an ear plug and a 1 mm radius tube from a computer cleaning duster. The opening of the ...
0
votes
1answer
75 views

Does spin degeneracy affect ideal Fermi gases in any way as T->Infinity?

In other words, given any system comprised of an ideal Fermi gas, in the high-temperature (classical) limit, are there any observable thermodynamic quantities (pressure, volume, energy, density, etc.) ...
2
votes
3answers
249 views

Why does the system move until equal temperatures are obtained?

In my college level thermodynamics class, the teacher gave us the example of a closed system which consisted of a box thermally insulated. A piston fully divides the box in two parts, and each is ...
0
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0answers
57 views

Can a volume of N2 be more negative than -14.7 psi?

Ok. I’m getting -30 PSI on a gauge calibrated at 0 for 1 ATM. Let’s say I have a chamber with a volume of 20L of N2 at 1 ATM. A vacuum pump that can pump to absolute vacuum let’s say 1X10^-10mTORR. ...
4
votes
1answer
143 views

How much atmospheric pressure (CO2) is required to carry iron oxide dust in the wind?

It is common knowledge that there are dust devils and dust storms on Mars. But can we demonstrate that the atmospheric pressure on Mars, which is 0.6% of the pressure we experience on Earth, provides ...
0
votes
1answer
123 views

Work needed to pump the balloons

Let's suppose that we want to pump the balloons underwater from the initial volume $V_0$ to the volume $V_1$. The pressure there equals $p_1$ and the atmospheric pressure is $p_0$. It is claimed ...
0
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1answer
99 views

How does the Cross section of a toy hovercraft affect on the time that it hovers? [duplicate]

My question is about a toy hovercraft - a balloon connected to a CD. I need to know about something. How does cross section of the pipe affect the time that the toy hovercraft hovers above the surface?...
-2
votes
1answer
159 views

How pressure effects on the time that a toy hovercraft hovers?

I'm working on a project and I have a question. How does the volume and pressure of the balloon affect the time the hovercraft hovers above ground? This relates to my earlier question where I ...
0
votes
1answer
44 views

Is the pressure * volume a constant in a balloon? [closed]

I'm having a question about balloons. I want to know that is the P*V of a balloon always a constant or no?
2
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0answers
256 views

How to calculate the strength of a silicon joint in an aquarium?

I'm building an aquarium, and i'm trying to answer the question "Will it catastrophically fail?" by reading the datasheet of the Silicon glue and doing a bit of calculation for worst-case scenario. ...
0
votes
1answer
30 views

what’s the water pressure at the surface of earth in Kpa? [closed]

I need to know this to solve a problem, but cannot find information on it.
1
vote
1answer
197 views

why doesn't liquid metal vaporize in a vacuum?

I am wondering why molten metal in a vacuum of electron beam and machines never turns to gas like liquid water does when exposed to a vacuum.
0
votes
1answer
390 views

If we dropped an object into the Pacific Ocean, would it completely sink to the bottom of the ocean floor or not?

Obviously if the density of the object is smaller than the density of water it would not sink at all. But I was thinking that, even if the density of the object is greater than the density of water, ...
0
votes
1answer
65 views

Capacitive pressure gauge under a change of pressure

I have seen in an article, that a capacitive pressure gauge made of two parallel plates with a dielectric material between with constant $K$ under an increase of pressure $\Delta P$, a Young´s modulus ...
0
votes
2answers
137 views

physical meaning of pressure derivatives

Is there any physical meaning of the first and second derivatives of pressure with respect to time? If this helps, I am considering ideal gases.
7
votes
4answers
1k views

Negative pressure, tension, and energy conditions

We have lots of common everyday experience with positive pressure, the canonical example is a gas. But other examples of positive pressure are easy to imagine: for instance, a solid that gets ...
2
votes
2answers
342 views

Existence of gusts of wind, an anomaly?

Enthusiast + Student, not a pro, so pardon my ignorance. How can wind possibly flow in gusts? The way I understand it, a gust is a pocket of air which hits you at slightly higher speed. But how ...
1
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2answers
169 views

Pressure-Velocity relation at a point in a flow

How can we relate pressure and velocity at the same point in a fluid flow? Why does pressure decrease with increase in velocity?
0
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2answers
296 views

hydrostatic pressure on a plane surface

I've been trying to calculate the amount of pressure on a wall of a rectangular structure, that is under sea watter. For example a dam. I can't come to see any example to be able to locate the ...
1
vote
1answer
1k views

How to calculate the increased pressure drop due to a restriction?

Assume I have a straight pipe with diameter D1 and a volumetric flow, Q flowing through it. The inlet pressure is P1 and the outlet pressure is P2. Now, assume I've added a restriction in the middle ...
1
vote
0answers
227 views

Regelation, ice cutting, and snowballs

Pressure decreases the melting point of ice, and applying pressure then releasing it will allow ice blocks to weld together by melting them and letting them freeze. See this video. The detractors of ...
0
votes
1answer
31 views

What is an expression/physical law that relates high frequency thermal fluctuations to gas pressure?

When a gas is compressed the 'ideal gas law' can predict what the increase in gas temperature will be. But that's just a mean temperature, right? At a quantum level the frequency of molecular ...
0
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0answers
93 views

How does a heated constant volume flow behave, for an expanding flow tube leading into the free atmosphere

I have a helium gas flow with a flow rate that has been set to a constant value ($0.3\,m^3/h$). It's streaming upwards in the picture, and beyond the upper big red dot position, it meets the ...
2
votes
3answers
127 views

How can Denver offer Hot Air Balloon rides?

So the air density in Denver is 1.0 kg/m^3. And heated air has the density of 0.95 kg/m^3. So adding the weight of the basket and balloon I don't understand how a hot air balloon could get off the ...
1
vote
2answers
99 views

Will a cloud form in a depressurized room?

If a room is depressurized will a visible cloud or mist form? I would expect it would, but when I apply a vacuum to a flask I see no cloud form inside the flask. Would a room behave differently than ...
13
votes
5answers
3k views

Why does my fireplace shoot flames out the front until I open my backdoor?

I have a natural gas fireplace with fake logs in it. I open the flue, turn on the gas for a couple seconds, and throw a match in. The flames kind of go up and out of the flue, but most of the flames ...
0
votes
0answers
78 views

Will increased air pressure increase efficiency of solute diffusion into a membrane?

Biophysics question: I have a container with a biological tissue inside of solution where the solute slowly diffuses across the membrane and binds inside of the tissue. If I were to put this unsealed ...
3
votes
2answers
3k views

Why is it difficult to cook food on mountains?

Why is it difficult to cook food on mountains? Is it because on increasing pressure boiling point of substance increase and on mountains there is less pressure so less boiling point. Then shouldn't ...
0
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3answers
340 views

Does acceleration affect the pressure?

I would like to measure the pressure inside the car ( by a pressure sensor or the altimeter). If we consider that the temperature inside the car is constant, do the car's velocity or acceleration ...
0
votes
1answer
417 views

How to calculate pressure using flow rate and pipe guage [duplicate]

On my farm I have a high pressure spring coming from the ground.it exits the ground from a 1 & 3/4" pipe.the water flows at a constant rate of 1 gallon per second (60 GPM.) Is it possible to ...
0
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1answer
50 views

Height dependancy when adding volume from below to a fluid column

Suppose there is a fluid column of height H and there is a screw already inserted from outside the column entering through the bottom of the column. The screw has a total length L and only 0.1*L is ...