# pressure's questions - English 1answer

1.780 pressure questions.

### Calculating the velocity of fluid in a pipe

2 answers, 53 views fluid-dynamics pressure
How can I calculate the steady state velocity of air inside a long pipe just knowing the pressure at the inlet and outlet?

0 answers, 11 views pressure fluid-statics
My points of interests is at point A and B. I want to investigate how much pressure is acting on this two points. (Ignore Atmospheric pressure and work in gage pressure). Since the oil will flow up ...

### 2 Can sound frequency create more ideal conditions for fire?

2 answers, 495 views thermodynamics pressure frequency air volume
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 ...

### How to derive the order of average intermolecular spacing of air molecules in the room temperature and standard pressure?

0 answers, 7 views thermodynamics pressure
The question is as above. I remember the answer to be of order $10^{-3}cm$. However I cannot see how to derive this order of magnitude from the contents of thermodynamics. Could anyone please help me?

### 2 Density solver for ideal mixture of real gases

1 answers, 303 views thermodynamics pressure density
I am referring the paper on GERG-2008 equation of state. I am interested in calculating the properties of ideal mixtures of real gases. The GERG-2008 EOS is in Helmholtz free energy and hence the ...

### 3 Why does frequency of collision increase as volume decreases?

Today I was presented with the following scenario: A syringe with one end sealed and with a frictionless piston is dipped into cold water. What is the change in frequency of collision(ie, more or ...

### 1 Why does the gas in Sun's outer layer not expand?

Since in the outer part of sun it consists gases. Why don't the gases expand due to heat? This was asked by my friend. And he said that the gases are attracted by the plasma layer by a force. So the ...

### 2 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 ...

### 1 Pascal's law-Glass Flask Experiment(doubt)

This image was of my book and written below this image was that when the piston is pushed down, it is observed that liquid flow out with equal pressure from each hole.But, I think that pressure at the ...

### Maximum pressure applied by finger [on hold]

1_What is the maximum pressure on pascal that can applied by finger on surface? 2_Also what is the maximum pressure can applied by hand palm grip? for example maximum pressure that generated by ...

### Why does the water pressure initially drop then stabilize when pressure testing a valve?

0 answers, 17 views pressure water air
Sometimes the dropping goes on so long(10-15 minutes) that the test is thrown out and the valve is opened and filled with water for a longer period of time. Pressure testers claim that it is because ...

### 1 Will flow rate always increase if the pressure drop across piping system is decreased?

3 answers, 1.662 views fluid-dynamics pressure flow
I have a test stand that is used for testing hydraulic pumps. We are adding a pump that we have never tested before and we are getting low flow readings. Will increasing piping to one size bigger than ...

### What's happening if we vacuum an air that exists inside aclosed system?

Excuse me, I have a closed system and wanted to vacuum an air that exists inside it, so what is happening with temperature inside that system ? Is it increase or decrease ?

### How to calculate air flow from a pressurized tank?

I am writing an app that deals with simulated air brakes, and I need to simulate the release of air from one container of a given pressure into another container of a lower pressure. It doesn't have ...

### 2 Soap Bubbles and Laplace's Law - contradicts intuition

1 answers, 317 views pressure surface-tension
What happens to a soap bubble as the outside pressure is increased? Imagine you blow a soap bubble at atmospheric pressure. The bubble equilibrates to some radius, $R_{0}$, with some internal ...

### 1 Why pressure standing waves have different nodes location with respect to the corresponding displacement waves?

In acoustics the pressure wave has a $\pi/2$ phase difference with the displacement wave. But I do not understand how this leads to a different position of nodes of pressure inside a tube with ...

### statistical definition of the temperature, the thermal energy and the pressure for an non-ideal gas

I recently realised that my definition (and understanding) of the temperature was only valid for a ideal gas: $T=\frac{2}{3 k_B}\int (u-v)^2f(v)dv$ where $u$ is the mean (or global) velocity of a ...

### 1 How do I calculate the height of a given that a bubble rises from the bottom of the lake to the top of the lake? [on hold]

I am stuck on a physics problem which involves calculating the depth of a lake given that a bubble increases two times in volume as it rises from the bottom of a lake to the top of the lake. The ...

### Dark matter pressure

Dark matter is suppose to form large halos of unknown yet type of particle with a specific density density profile. Does the dark matter halo can be viewed as a fluid of particles with density and non-...

### What is the basic difference between absolute pressure and gauge pressure? [duplicate]

What is the basic difference between absolute pressure and gauge pressure?

### 15 Gauge pressure vs. absolute pressure? [closed]

6 answers, 709.980 views pressure terminology
What are the key differences between Gauge pressure and absolute pressure? Are there any other forms of pressure?

### 2 Sonic Boom in Aircraft and Spacecraft

I would like to know why aircraft, and spacecraft produce a double sonic boom on breaking the sound barrier. A while ago, I thought I got it, as there’s a start and finish point to every vehicle. ...

### 2 Does Fick's law of diffusion applies between mediums of different pressures with no membrane?

1 answers, 58 views thermodynamics pressure diffusion
Imagine a stainless steal container with an unsealed lid that contains normal air, inside a room containing normal air. Now, pump a steady flow of CO2 in that container, bringing it to positive ...

### 5 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 ...

### 1 How Temperature, Pressure and Altitude are related in the atmosphere?

2 answers, 1.911 views pressure temperature atmospheric-science
I'm looking for an approximation for the temperature of the atmosphere at any height and pressure. Both altitude and pressure are known variables, I've derived this equation using maxwell's ...

### 2 How to calculate altitude from current temperature and pressure?

2 answers, 6.188 views pressure temperature
In a certain project, I need to calculate the altitude of the current location given the current location temperature and current location pressure. Temperature, pressure and altitude of a 'reference-...

### 9 Jumping sewer lid - WHY?

7 answers, 4.256 views pressure nature
Intro: Few hours ago, there was a storm. We heard some constant banging which couldn't be explained by thundering. Then we found out, it was a sewer lid jumping. Maybe it's normal in other parts of ...

### What is the resistance of an object travelling through static fluid at different pressures?

1 answers, 20 views fluid-dynamics pressure drag
I'm interested in the resistance a body feels as it travels through a static fluid in a tube (of a fixed radius), at different pressures. I would assume that as the pressure is reduced, the ...

### -2 Life around a different element from Carbon [closed]

On Earth, life developed around Carbon (and Hydrogen and Oxygen). I guess this depends on the availability of those elements, but also on the spectrum of radiation and Temperature and Pressure. Under ...

### How to calculate increase in pressyre from LN2 phase change

0 answers, 15 views pressure ideal-gas gas volume liquid-state
I am trying to calculate the increase in pressure caused by liquid nitrogen when it changes from liquid to vapor within a closed, constant volume at atmospheric pressure. The liquid nitrogen fills 100%...

### 1 For a fluid travelling in a tube, if the pressure is decreased at a constant temperature, how does it affect the velocity and fluid density?

I am interested in understanding the relationship between pressure and velocity, as well as pressure and fluid density. I know that the principle of Bernoulli states that there exists a relationship ...

### Why isn't dynamic pressure actually a pressure? [closed]

Take for example flow through a pipe. Even though dynamic pressure is not acting on the sides of the pipe because the molecules are travelling parallel to the pipe walls, it should still be imparting ...

### 3 Dispersion of Water: A Swimming Pool Conundrum

1 answers, 51 views waves pressure water
The following question came up in a swimming pool: The pool has a jet that releases water below the surface. When I put my right hand in the water, several feet away from the jet, I can feel the ...

### Stagnation Pressure Loss through Sudden Area Expansion

I was doing some reading in an textbook on gas turbine propulsion physics, and I came across an interesting formula. Consider a duct with cross-sectional area $A_1$ that encounters a sudden area ...

### 2 Does Friedmann fluid equation prove that energy of the fluid is not conserved?

The Friedmann equation in question is:$$\dot\rho + 3H \left(ρ + P\right) = 0 \,.$$ I’m a layperson so I don’t know why this equation is sometimes called fluid equation, energy conservation equation, ...

### -3 Pressure unit computation (feet of mercury, but applies also to foot of water..) [closed]

1 answers, 34 views pressure units unit-conversion
Grr this question makes me crazy. Here you can see that ftHg = 13595.1 kg/m3 × 1 ft × ɡ0 = ≈ 4.063666×104 Pa. (= 40636.664 Pa) https://en.wikipedia.org/wiki/Conversion_of_units (Pressure or ...

### 1 Thermodynamics Work Done At constant pressure and charles law

1 answers, 1.010 views thermodynamics pressure ideal-gas
If we fix a piston in the mouth of a cylindrical container in such a way that the piston settles when the pressure from outside the piston is equal to that of the gas within the container, and ...

### 2 How does the bulk modulus of air change with rising pressure?

2 answers, 7.747 views pressure ideal-gas volume fluid-statics
I can't seem to find the answer to what should be a trivial question: I have a rigid air-tight container of fixed volume and I am pumping air inside. The pressure is increasing (very slowly) from ~...

### Lifting gas pressure inside rigid airship

1 answers, 52 views pressure gas
I guess I'm asking the wrong question. Let me rephrase with another example. Assume I have a bottle of liquid hydrogen. It's connected to a non-porous balloon with no elasticity made of, say mylar. ...

### Specific Volume vs Temperature Graph

1 answers, 31 views thermodynamics pressure temperature
When looking at a graph of comparing temperature and specific volume, we see that for increasing pressures, the boiling point increases and that the length of the saturated liquid-vapor line decreases....

### fluid statics doubt (regarding free body diagrams)

why does the pressure exerted by liquid on side walls increases with depth? please explain in detail.Thanks in advance

### 1 Static Pressure in a Venturi vs a Free stream

We seem to have two conflicting measures of pressure in a Venturi siphon open to the atmosphere,$\hspace{100px}$. Bernoulli's principle says that, by energy conservation for a steady flow $Q$, the ...

### 1 Bubble with varying pressure over surface

I was wondering if it's possible to have a soap bubble with a varying pressure over its surface? That is, such a bubble would not have constant internal pressure at all points. I am specifically ...

### 3 What happens to the pressure inside a tied-off balloon as the pressure outside the balloon decreases?

I'm almost 100% positive it would decrease, but my meteorology professor (who also teaches physics) says it will stay the same, because no air is escaping the balloon! Does the rubber of the balloon ...

### 2 What is fluid pressure?

I cannot understand the concept of fluid pressure. Consider a liquid molecule at some point inside a liquid vessel. All the other molecules which are in contact with this molecule will exert normal ...

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

4 answers, 407 views pressure hydrostatics
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 ...

### Compression and expansion of solids vs fluids

Why is it that solids on compression [As in striking a hammer etc.] heat up, but liquids and gases on compression [Pressurizing liquids causes them to freeze or gases to liquify] cool down? Can ...

### is boiling point of the gas cause cooling in expansion process of refrigeration?

I have a doubt about expansion process. Some people say it's an adiabatic expansion, but other say it's something related to the nozzle. What is the actual cause for cooling in expansion process? ...

### Pressure of the same mass of fluids of different densities?

Suppose I have 2 fluids of different densities, and I pour the same mass of each fluid into 2 identical cups. I feel like I'm confusing myself here — on one hand hand, both cups contain the same mass ...

### 2 Why is steam-cooking slower at higher altitudes, where water boils at a lower temperature?

1 answers, 244 views pressure temperature water
This question comes from a chemistry test that i got back. I'm posting this on physics.stackexchange because i feel that i don't get the physics side of it. We learned that temperature increases the ...