Force per unit area.

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2answers
19 views

Reason for fluid pressure

What is the physical reason that high pressure regions (say, of air or water), want to expand into low pressure regions? What force is causing them to "equilibrate" the pressure? The only thing I can ...
0
votes
1answer
14 views

What does “ambient atmosphere of 20 mu” mean?

I've read through a publication from 1960 which discusses oxygen annealing. It shows a the following graph. What does the "ambient atmosphere of XY mu" mean? What is a mu atmosphere? taken from: ...
-1
votes
1answer
23 views

Curious about headphones [on hold]

So I'm trying to learn more about headphones. I have a small piston that is in a small sealed volume (the earcup, say it is $25\, cc$). And there is a front volume between the piston and the ear (...
2
votes
0answers
36 views

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 ...
-1
votes
0answers
21 views

Find the required power by specific time to reduce volume in an air filled cylinder that have a hole? [on hold]

How to calculate the required power by specific time to reduce volume in an air filled cylinder(or to push piston in air filled cylinder) that have an orifice? Another side of orifice is world ...
0
votes
1answer
22 views

Concentration change due to different pumping efficiency

I send a mixture of two gases (5% (v/v) initial concentration) into a chamber. The chamber is pumped to a low pressure, but the efficiency of the pumping for both gases is not the same (because of ...
1
vote
2answers
48 views

Force of water hitting a wall [closed]

If you had a 8" pipe with 500psi stream of water exiting it and hitting a wall at 90 degrees 8 feet away, what would the force of the water on the wall be? Thank you all. Non-mathematician.
1
vote
1answer
56 views

Bernoulli equation and pumps [closed]

I have a doubt on the use of Bernoulli equation for pumps. Consider the situation in the picture. I marked different points: $1$ on the surface of first tank, $2$ in the exit from first tank, $3$ ...
4
votes
2answers
155 views
+50

Static vs Dynamic pressure

According to Bernoulli's law, the narrower the tube where the fluid is flowing the lower its static pressure and the higher its dynamic pressure. Does this make any difference? If the dynamic pressure ...
0
votes
1answer
66 views

A fan is connected to a pipe, what happens to the airflow after the pressure drop?

Overview I am trying to find out what happens to the air flow within a pipe if a fan cannot generate the required pressure to overcome the friction within the pipe. After much research I am aware ...
0
votes
1answer
63 views

Using the ideal gas law to figure final pressure [closed]

I'm studying for the GRE and I'm happy with Charles', Boyle's and Gay-Lussac's laws. I'm doing some questions on the ideal gas law. Please hear me out. This may come across as a homework style ...
2
votes
0answers
33 views

How can matter be squeezed extremely dense [duplicate]

I'm fairly new to physics and currently reading A Brief History of Time by Stephen Hawking. Hawking is talking about black holes being the size of a few miles containing the mass of multiple times the ...
0
votes
1answer
34 views

Matching Bernoulli equation and Hagen Poiseuille law for viscous fluid motion

I thought that Bernoulli equation could be used only in the case of non viscous fluid. But doing exercises on 2500 Solved Problems In Fluid Mechanics and Hydraulics (Schaum's Solved Problems Series) ...
0
votes
2answers
58 views

Reversible processes in which mechanical or thermal equilibrium is not reached

The definition of a reversible thermodynamic process requires in any instant the mechanical equilibrium (equal pressures) and thermal equilibrium (equal temperatures) of the system in a quasi-static ...
0
votes
2answers
50 views

What is the difference between real value and abs value? [closed]

I am confused here, though I have been reading about it for years. What is the difference between a real value and an absolute value? For example, when do we take the absolute value of pressure or the ...
1
vote
3answers
72 views

Pressure just before the hole in a draining tank

I get extremely confused in fluid dynamics problem where the pressure in some points is required. Consider the ideal fluid in the tank in the following picture. I would like to understand what is the ...
4
votes
2answers
142 views

Weight Distribution of granular piles

I was recently at a farm watching piles of grain being formed in the shape of enormous cones. Each of these grain stacks weighs in excess of 50 tonnes. I am not a physicist but I am very curious as to ...
0
votes
3answers
46 views

Work done on gas problem with movable set

I found two different version of an exercise where the work is considered in a different way. Consider a gas in a tank divided in two parts by a movable set. The set in $B$ is also movable. If a ...
3
votes
3answers
76 views

Fluid mechanics paradox: The force needed to 'balance' a fluid using a piston

We know that the pressure in a fluid (like water) is dependent on the depth. Consider this example: For the first setup, solving the pressure at the bottom yields $P_1 = \rho gh = 1000kg/m^3 \bullet ...
0
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3answers
27 views

Application of Bernoullis identity for problem concerning hole in a container

Consider the following problem: We have a container of water with a hole on the side, and we want to determine the velocity of the stream coming out of the hole (at $S_2$): If we suppose $S_1>&...
1
vote
2answers
45 views

Is it possible to make iron shavings to be dust? [closed]

I'm considering how to separate iron shavings from iron. In the picture, there are some iron chunk and iron shavings. The problem is iron shavings are not dust. I want to make the iron shavings to be ...
0
votes
2answers
54 views

A dead body floats with its head immersing in water . Why?

I found this question in my practice book . I want to know about it .
0
votes
0answers
28 views

How does it come that a soda still sparkles out of the bottle, even after I can squeeze it allready?

Just noticed this right now. I have known for long time that of course, shaking a sparkled soda causes it to harden and build up pressure. When one now carefully opens the bottle it starts to ...
-2
votes
1answer
40 views

Space vacuum power

How strong is the vacuum in space? If possible in mph, or other easy to understand measurements...as someone else asked, "if you took a bottle of air into space and opened it, where would it go?" I'm ...
0
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0answers
24 views

Air pressure equalisation

I'm programming a physics simulation and have the air pressure impact the movement of rigid bodies in the system. I know how to (approximately, both for simplicity and performance) specify bodies' ...
0
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0answers
30 views

How can one calculate the drop in air temperature associated with a rise in its humidity?

Background: I wish to model the effect of an evaporative cooling system in a humid, tropical environment to be used as a feasibility study. Anecdotally, such a system would be ineffective, but I would ...
0
votes
1answer
45 views

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 ...
0
votes
0answers
12 views

Law of Floatation [duplicate]

We know, law of Floatation states that A body floats in a liquid if it can displace the liquid equal to its weight. But how can we derive this mathematically. Can anyone help me for this; Derive ...
2
votes
3answers
34 views

The effect of surface area on the pressure exerted by gases

In a video about the relation between pressure and volume on Khanacademy, Sal says that on increase in volume the particles hit the wall less often because the volume has increased and the surface ...
0
votes
1answer
36 views

find the density of water only by its pressure?

Is it possible to find the density or specific volume of water, by only knowing its pressure? Or we need to know its temperature as well? I can't find any relevant table, so can you advise me please? ...
9
votes
1answer
123 views

Why does paper explode when compressed?

Various videos online show paper/card suddenly releasing energy in an explosion like way and transforming into a brittle material when put under sufficient pressure from presses. Examples are shown ...
1
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0answers
27 views

Why does a band of paper I hold between my hands never breaks in the middle?

If I hold a band of paper with my digits and thumbs and start to pull, the band never breaks in the middle, but on one of the sides where I've put my fingers. Why is this? Has it to do with the ...
-4
votes
2answers
68 views

Pressure exerted by a gas and the ideal gas equation

While determining the pressure exerted by any gas at a temperature why do we not consider the surface area of the container in which it is kept? We say that : P=nRT/V, where, n is the no. of moles, R ...
1
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0answers
22 views

Heating of mixture of gases with one gas barely above its boiling point

What happens when mixture of two gases is heated in a closed container? If one gas expands faster than the other and increases pressure of the container enough so that the boiling point of the other ...
2
votes
3answers
50 views

Gas pressure within containers [closed]

If, hypothetically, a gas had no inner pressure, and it was made to fill up a container. If, then, the pressure within the container was increased by filling it up with yet more gas, until high ...
0
votes
1answer
26 views

Can you pressurize a vessel to ambient pressure if the outside pressure is 0 psi?

let's say we have a vessel that is open to the atmosphere and is located at an altitude where the atmospheric pressure is about 0 psi. Then, we hook up a pressure pump and attempt to bring the ...
0
votes
2answers
49 views

Application of Bernoulli's equation to siphon

I'm trying to understand how to use Bernoulli's equation in practice. So I will make an example of where is my confusion. I found this great explanation on Wikipedia about the siphon, but there is a ...
1
vote
1answer
70 views

Raising a cut on your arm above your heart

I often read that when you have a deep cut on your arm, you should raise your arm to the point where the cut is above your heart. This should reduce the amount of blood loss because less blood reaches ...
1
vote
3answers
64 views

Pressure Drop in Water Fountains

In first grade, my class made a list of things that our school could improve on. One of the things on the list was to increase the water pressure in the drinking fountains because it was very poor and ...
3
votes
1answer
28 views

Consequences of general equation of hydrostatics $\nabla p= -\rho \nabla E$ in terms of surfaces where $p$ and $E$ are constant

I'm facing difficulties in understanding the consequences of the general equation of Hydrostatics in the case of conservative forces. $$\nabla p= -\rho \nabla E\tag{1}$$ Where $p$ is the pressure, $\...
3
votes
0answers
39 views

Chemistry of water under pressure [closed]

What is the structure of water under extreme pressure, like the bottom of the ocean on a moon like Europa.
-4
votes
1answer
31 views

Fluid mechanics : find the abs. pressure in mil. of Hg [closed]

Problem: A vacuum of $25\, kPa$ is measured at a location where the elevation is $3000\, m$. What is the absolute pressure in millimeters of mercury? Solution: Through interpolation, $P_{atm} = 70.7\...
8
votes
2answers
133 views

Pressure standing wave nodes at the end of the open side of a tube

I do not understand why standing sound waves can be formed in a one-side or two-side open tube. Consider a one-side open tube. In particular how does the reflection of the wave at the open end occur? ...
0
votes
1answer
40 views

What happens if a cylinder filled with propane gas is connected to an empty one of the same size

Lets say I have 2 100lb propane cylinders. One of the cylinders is filled to its maximum capacity while the other is empty. If I connect them to each other via a high pressure hose in an upright ...
0
votes
2answers
98 views

Why do liquids exert pressure on the sides of a container?

What makes a liquid push against the walls of a container if the liquid is completely static? I was thinking a comparable situation would be a bin full of baseballs. Unless the balls were perfectly ...
3
votes
1answer
33 views

Force on a balls shell

Suppose we have a sphere with radius $r$ and the thickness of its shell is $l$. The pressure outside is equal to pressure inside which is $p$. Total force on the outside is: $F_o=pA_o=p4\pi (r+l)^2$ ...
1
vote
2answers
37 views

estimating deviations from ideal gas behaviour

How can one estimate the pressure at which argon atoms show deviations from ideal gas behaviour due to the finite size of the atoms? I have tried Taylor expanding the hard sphere gas equation: $$P'(...
0
votes
4answers
46 views

Pressure on the sides of a container?

Sorry if this is an incredibly basic question for these categories. Basically, I don't understand why I'm not getting these types of problem. I'm sure it's something really simple I'm missing. So let'...
0
votes
4answers
114 views

Why the pressure in liquids only depends on the height?

look at this picture : and also look at this one: imagine that the surface area of both is the same and both of them are full of water. My question is that why they both are pressing the beneath ...
1
vote
0answers
74 views

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 ...