# Questions tagged [pressure]

Force per unit area.

2,023 questions
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### Mercury Barometer

Why Mercury surface is flat instead of convex at 760mm Hg level in Mercury Barometer? refer the image attached. note that At top it is a vacuum and surface tension = (pi-po)r/2.
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### Can air pressure be applied equality to a rail to lift a carriage?

There is a transport design that has a carriage suspended from a rail (A) that is levitated by pumping air through holes (B) into an area with the intention of levitating the carriage so that it can ...
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### Tone production in Irish Flutes?

Since it's about a technical issue, I thought that this question would fit in here the best (as opposed to the music.stackexchange-site): I'd like to know how tone-production in an irish (wooden) ...
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### How is sound affected by gravity?

How would sound be different on a planet with a stronger gravitational field? My reasoning leads to sounds of the same wavelength having higher frequencies - is this correct?
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### Solving for work without being given pressure [on hold]

The following is an MCAT question I'm not sure how to approach. We have to solve for work without being given pressure. This is how far I've gotten: F=PA, Thus, W=Fd, W=PAd. Ad=deltaV, so W=PdeltaV. ...
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### Is this working by communicating vessels?

https://www.youtube.com/watch?v=JzuamK0AyC4 I think the first 2 bottles are working by communicating vessels because i think that the third bottle is with atmospheric pressure and since the second ...
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### Diameter to prevent water flow into a closed-end tube?

Imagine I drill three holes of different diameter into a large block of plastic but the holes don't go all the way through. (They form three close-ended tubes, see the image.) I then submerge the ...
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### How does the Torricelli barometer create a vacuum at the top of the tube?

Hi everyone! Can someone explain to me how does the Torricelli barometer creates a vacuum at the top of the tube? And how does it work?
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### Does increasing pressure increase or decrease latent heat of vaporisation?

I found some say increasing pressure increases the latent heat of vaporisation (What is the effect of an increase in pressure on latent heat of vaporization?). This doesn't make sense to me because ...
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### Volumetric Flow with Air Compressor [on hold]

If I have a 5 gallon, 125 psi air compressor and I connect that to a pvc pipe with holes in it, how would I go about determining the amount of air flow through each hole in that pipe. It might be ...
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### What does it really mean by “faster flow, lower pressure”?

My primary school physics textbook trys to brainwash me with the idea that a region in a fluid with fast velocity (often) has lower pressure than a region that flows slowly. Examples of this include ...
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### The variation of density of a liquid in a cylindrical container due to it's bulk stress [closed]

A vertical cylindrical vessel contains 1ltr. of water having column height of 60 cm. Density and bulk modulus of elasticity is given as 10³kg/m³ and 2×10^9 N/m² respectively. What will be the change ...
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### In a spinning tube, how low can the vacuum in the center be?

If you put a gas in a tube, and spin the tube [edit: along the axis of the cylinder], you will get a centrifuge. What's the maximum pressure differential between edge and centre? Asked another way: ...
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### If a steam injector increases pressure by lowering temperature would a 'refrigerant injector' work using ambient heat?

In a Giffard type steam injector, boiler feed water is added to the boiler by passing steam at around 10 bar/180C through a converging/diverging nozzle, collecting cold water in the vacuum at the vena ...
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### Phase difference between displacement wave and pressure wave in longitudinal waves

As the Mathematical treatment yields, the pressure wave leads the displacement wave by $\frac{\pi}{2}$. But I want to ask why is it so? According to me, supposing if the displacement wave is a sine ...
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### Pressure in irrigation water pipe

I would like to know the pressure at the bottom of the pipe which I use for irrigation purpose. The land is step cultivated and the pipe goes slanting for the length of 140 meters and the top height ...
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### How to calculate the actual pressure in chamber with reduced pressure but at increased temperature?

I would like to find out the actual pressure in a chamber (constant volume) where the pressure within is reduced to 1.5 kPa but with increased temperature to 65˚C. How to calculate this? Assuming 0....
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### Low Air Pressure

Can we create low air pressure artificially in a system to make the wind blow towards the system from the higher normal air pressure in vicinity ?
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### Grooves on water tank

Why are there grooves on almost every water tank? Just typing water tank in Google images would reveal what I am talking about. And here is a sample picture! I think it would mostly be regarding ...
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### Water beyond 10.3 metres [closed]

Using a centrifugal pump, you can only pump upto 10 metres. Thats fine. But, Can't i pump water beyond 10.3 metres by placing the suction head exactly at 10 metres( or below that) and extending the ...
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### What will happen if my room is half filled with dry ice? [on hold]

Suppose we have a sealed room, the room is a cube, half the room is filled with dry ice. What will happen when the dry ice sublimates to CO2, will the pressure of the room increase dangerously as the ...
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### Laplace's law derivation

I'm reading a biology paper which uses LaPlace's law in the analysis. Basically the tension within a spherical pressure vessel is half the product of the radius and pressure. I'm trying to understand ...
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### Water thru a small hole

If I were to fill a 700c 25mm road bike tire with some water and pump the tire to, say 100psi, and punch a tiny hole in the tire, the water will start to spray out. My question is: does the water ...
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### Does the total energy in a volume (gas) increase linearly with increases in pressure?

If a volume has a certain pressure, then double that pressure at another time, is the total energy stored doubled? I'm sure this has to do with thermodynamics and if I remember correctly there is a ...
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### Amount of pressure embodied by a pressure wave (sound)?

I'm looking into a way to calculate the pressure by which a sound wave at close proximity to the target object impacts. My research led me to this physics site (http://hyperphysics.phy-astr.gsu.edu/...
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### Pressure Difference in a vacuum environment

We all know pressure is relative, and the pressure of a containment changes with change in its surrounding pressure. Now comes the obvious question: If I have a water balloon half filled in a ...
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### Viscous flow through a concave tube

Consider gravity-driven incompressible flow through a concave tube with known radius $R(z)$, where pressure is atmospheric $P_a$ on both ends: How does the viscous pressure distribution $P(z)$ ...
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### Do viscous and inviscid flow have opposite effects on pressure?

Consider flow through the converging and diverging portions of a tube with varying radius: In inviscid flow, Bernoulli's equation states that velocity at the throat will be the highest, so this area ...
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### Bubbles in a Pipeline 2

This question has kind of been asked before here, but aren't the gas bubbles in the pipeline also a moving fluid and so as they get constricted shouldn't their pressure decrease too. If so how are ...
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### What is the pressure of water after entering atmosphere? [closed]

I was wondering if water exits from the pump and reach the ground, is the pressure of the water at the point of the ground be 0?
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### Atmospheric pressure in a closed container

it's my first post here but I just have a quick question regarding my fluid mechanics assignment. There's an inverted manometer setup like in the photo which is a closed system. It's given me ...
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### Phase diagram of a fluid

How is it look like the phase diagram of a fluid in density-pressure plane? I came across the phase diagram in Pressure-temperature plane most of the time. But I can't find the phase diagram in ...
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### What is the volume of liquid propane consumed when measuring gas flow at a given pressure?

We have a building with a large propane cylinder that distributes propane to different sources within the building. When the cylinder is filled, the propane is compressed to a liquid, and our bill is ...
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### Why do we use pressure instead of force for liquids and related measure?

I have been reading about pressure and wasn't able to find the actual meaning of pressure except for the formula pressure = force/area. And when I began to study Boyle's law, need to understand the ...
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### Contact Force of Inflating Balloon

I am trying to roughly model the contact force an inflating balloon would apply on the skin. The idea is the balloon would be constrained between an in-extensible layer on one side, and the surface of ...
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### Why isn't Argon's heat capacity ratio constant with temperature?

The Wikipedia Heat Capacity Ratio page claims that Argon has a different ratio at -180°C, that would make it the only noble gas that doesn't always hold a ratio of ~1.660, why is that ?
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### Is the Earth Atmosphere Model at this NASA site wrong?

I've been trying to get a decent numerical approximation (curve fit) of Earth's Atmosphere Model, and found what I was looking for at this NASA's web site. However, when checking some basic ...
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### Effect of increased air pressure on water pressure in sealed container

Imagine I have a plastic bottle filled most of the way with water and with a bicycle pump attached to the top without any leaks... If I increased the air pressure in the top of the bottle to, say, 30 ...