Force per unit area.

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2
votes
2answers
347 views

Dynamic water pressure from flow and diameter

I've to test some fire hydrants and need to get the dynamic pressure. For that I know I can use a Pitot tube but... I don't have. After Googling a lot, I found two formulas allowing to compute the ...
1
vote
2answers
46 views

Atmospheric pressure on a flat object

Consider a 10 inch by 10 inch sheet of paper lying flat on the ground. If atmospheric pressure is 15 pounds per square inch (sea level), then there is 1500 pounds of force acting downwards on the ...
-1
votes
1answer
45 views

How long will pressure exist in this case?

I'm currently fabricating my project, which currently exists only on paper, and there's one question to which I have stumbled today. Suppose, that I have a pressure vessel capable of holding upto ...
3
votes
3answers
216 views

How does vasoconstriction/vasodilation of arterioles change blood pressure?

Background: I am coming at this question from an electrical engineering background, and I feel like I am missing certain assumptions that are going into the statement found in my physiology textbook, ...
0
votes
0answers
23 views
0
votes
3answers
53 views

Does a gas in a container lose kinetic energy?

When a gas is in a container, it frequently collides with the container wall, exerting pressure. However, with a collision, kinetic energy ought to be transferred from the gas molecule to the ...
1
vote
2answers
81 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?
-1
votes
2answers
50 views

If you place a filled water bottle at the bottom of the Mariana Trench, how does the bottle stand the enormous pressure?

The pressures are akin to an entire train pressing down on you. How does the water bottle stand this pressure? And yes, the water bottle will stand: How else do the creatures at the very bottom of ...
0
votes
1answer
18 views

If you brought a hollow one-inch cube of steel filled with air into space, would the air exert a pressure of 14.7 psi on the cube?

In my thought experiment, since air exerts $14.7$ psi at sea level, the air within the cube of steel should exert the same pressure outward, $14.7$ psi. Right? The whole thing about balanced air ...
0
votes
0answers
11 views

What happens if you blow at a paper wad sitting at the doorway of an airtight room?

Sounds like a hilarious scenario, but this is why it got me thinking: A common experiment demonstrating air pressure is to put a paper wad at the mouth of a bottle, and then blow into the bottle. The ...
6
votes
1answer
705 views

Could a vacuum airship be possible? [duplicate]

According to Wikipedia, a vacuum airship is a hypothetical airship that is evacuated instead of using a lighter gas. Really, once I first saw this, I thought, "Why did I never think about this ...
-3
votes
0answers
14 views

Force, Pressure and Friction [closed]

Calculate the pressure at the bottom of a fresh water lake of depth 10 m. Atmospheric pressure = 76 cm of mercury and density of the mercury.
0
votes
0answers
19 views

Pressure gradient - derivation for air stream

I need help clarifying the statement made here that $$dp = l\frac{dp}{dx}$$ $\frac{dp}{dx}$ is an infinitely small change in pressure at some point x. $dp$ is the total change in pressure between ...
2
votes
2answers
114 views

Why do unused tires lose their pressure?

I have two tires, and I filled both with air at the same pressure. I used one for one month and kept the other one unused. Surprisingly, at the end of first month I found that the first tire had ...
-1
votes
2answers
51 views

How do I calculate the weight that PSI can lift?

Imagine that there's a force that is given to you in $psi$, say $1450\ psi$. And there's some body of weight say, $100\ kg$. What I want to know is that, how much $psi$ will I need to lift the "body" ...
-1
votes
1answer
20 views

what is the pressure that a sonic wave actually creates?

We know that sonic waves across atmosphere are basically areas of high and low pressure. But I couldn't find how much is that pressure. There are online calculators to calculate the sound pressure, ...
0
votes
0answers
20 views

What happens when heating water in a pressure vessel?

Suppose that I take a pressure vessel that can hold up to 2000PSI force. Now I fill it with water (not completely, but around ~90%) and now I start to heat it with direct flame, LPG gas cylinder. What ...
0
votes
2answers
34 views

what is the effect of a sound wave at the opposite side of its direction?

We know that a sound source produces a sound wave and a high pressure area is followed by a low pressure area, while they travel with 300m/s. My question is, if the sound source travels with 50m/s in ...
-1
votes
0answers
12 views

Tapering Mercury Barometer

I am curious if the height of the Mercury column inside a Toricellian Mercury Barometer be the same if we use a tapering / stepped (unequal inner diameter [ID]) glass tube as depicted in the image ...
0
votes
0answers
15 views

Slow sustained liquid movement in a vacuum

Can water or any other liquid be made to “simmer” or “low boil” (slow sustained liquid movement) in a vacuum as opposed to go from liquid to all out boil when the vapor pressure is equal to the ...
1
vote
5answers
5k views

Water pressure calculation for a volume of water at a given height

I'm looking to create a rain harvesting system. I have a 275 gallon IBC tote that is 48" x 40" x 46". I have an adapter for a 3/4 garden hose at the bottom of the IBC tote. I'm trying to figure out ...
0
votes
0answers
18 views

sound waves and atmospheric pressure

Is it possible to use sound waves (ultrasound/infrasound or whatever) in order to make some space have lower atmospheric pressure? Or maybe another way to achieve this? I was thinking that maybe sound ...
3
votes
3answers
3k views

How to calculate pressure loss due to water leakage from a hole in a pressurized unit

I am trying to develop a method for calculting the rate of pressure loss from a small hole in a pressurized vessel full of water (small air pocket likely at top of vessel). I've found a formula for ...
0
votes
2answers
108 views

Given a slanted pipe

Question: I have a pipeline that is tilted. I know the length of the pipeline, and the pressure (90psi) that is felt at the very bottom. I'm trying to find out how much liquid has leaked out if the ...
1
vote
0answers
24 views

Connection between gas flow rate and diameter of tubing

First time poster, long time troller and curious student. I have a bit of a conundrum that I would love some input on... Here's the problem. I have an air flow system is under constant pressure of ...
3
votes
1answer
138 views

Is this the correct way to I combine multiple interdependant pressure readings?

I want to measure the density in different layers of a suspension. To do this I want to place pressure sensors at different heights. Let's assume that the sensors are not by orders of magnitude more ...
1
vote
1answer
47 views

Determine fan sound (dB) based on its rotational speed (RPM)

I am trying to find the sound amplitude or level produced by a fan, knowing its RPM. Is there a simple formula for it? What other parameters does it depend on? Assume I have all the fan properties, ...
1
vote
3answers
46 views

Calculate pressure with the ideal gas law or $\rho gh$?

In a container the pressure on the walls due to a gas can be calculated using the ideal gas law $\bigl(pV=NRT\bigr)$. However, for a column of water, or the pressure at earth's surface due to a ...
2
votes
1answer
155 views

How to calculate the amout of time for oil to get out from a pneumatic cylinder?

I have a system. You can assume it is just a 1" diameter steel pneumatic cylinder (1 foot long). Assume we ignore the bore size issue at this point. One chamber is filled up by oil (6" of volume), ...
0
votes
1answer
28 views

Question about pistons and how their volume is affected by particles?

I can't find an answer to this anywhere. When pressure is maintained in a piston and an ideal gas is injected into it (again, with no change in pressure as it is injected) the piston is displaced ...
0
votes
0answers
16 views

is there any element or material that ionized when pressure is applied to it?

I want to know if there is any material, that produce free electrons and ions when it undergoes to high pressure.
0
votes
0answers
17 views

Is surface tension the result of a pressure drop over the air-water interface or visa versa, for a two sphere system?

For a liquid bridge between two spheres the Young-Laplace equation states that: $\vartriangle p= \gamma\bigl(\frac{1}{R_1}+\frac{1}{R_2}\bigr)$ where $\vartriangle p$ is the capillary pressure ...
1
vote
2answers
129 views

Silicone tube with three holes, flow rate, pressure

I have a silicone tube -- a saline solution flows in from one end, and then flows out of three holes of equal diameter and equal distance from each other that are along the side of the tube. What can ...
0
votes
1answer
749 views

Pressure loss in a syringe

I'm currently working on a problem which is really giving me some issues. The problem concerns the force required to expel water from a syringe. We have a 20 ml syringe (which is $2\times10^{-5}$ ...
2
votes
2answers
119 views

Expression for Atmospheric Pressure with Altitude, including Tidal Forces

Is this simple to obtain? I've tried to modify the constant-gravity model to use the $GM/r^2$ form instead, but my result was shown to be wrong with some testing. Constant Gravity Model You can ...
4
votes
1answer
199 views

Bubble in a pipeline

I am just thinking about this phenomenon: We have a horizontal pipeline with a flowing liquid, which contains a small bubble of gas. How do the dimensions of this bubble change when it reaches a ...
6
votes
2answers
2k views

Why is pressure in a liquid the same in all directions?

I'd like answers both in the more intuitive side an on the more precise side. Thinking of water as "cubes" of water, for example, would allow pressure in the z axis to be independent of the y or x ...
6
votes
5answers
1k views

Is there a depth at which a human body, with lungs full of air, will no longer float?

I was watching a special on divers who dove down hundreds of feet without tanks or gear. The show referred to a depth at which the diver was no longer buoyant and would actually sink, even with lungs ...
14
votes
9answers
4k views

How to emulate 40ft (12 m) of water? [closed]

I am part of an underwater robotics team, and our next year's challenge requires us to compete at a depth of 40ft. We don't have any pools nearby to test in, so I want to emulate this 40ft of pressure ...
-2
votes
1answer
101 views

Where does a sparkly (CO$_2$) water bottle have more presure [closed]

Where does a sparkly (CO$_2$) water bottle have more pressure? At a higher altitude (7000 feet) or under sea level (-8 feet)?
1
vote
2answers
48 views

Is this a case of the “venturi effect”? What's behind the “Venturi effect” actually?

Some dinghy sailboats have a hole in the bottom of their deck used to automatically bail out water after a capsize. bailer of the laser sailoat The mechanism only works if the boat is moving. The ...
2
votes
1answer
72 views

Will changing the pipe diameter reduce the pressure head loss?

I have this system installed in my house (fig 1), and I'm having problems with the shower. I want to know whether, if I change the PEX tubes shown in red from 1/2" to 1" as shown in fig 2, I will have ...
2
votes
0answers
219 views

How do I calculate the energy balance of a trompe?

I was quite fascinated by the concept of an ancient type of air compressor, called a trompe. It entrains air bubbles into a falling stream of water via the Venturi effect, and extracts the air at a ...
1
vote
1answer
1k views

Pressure vs Volume Calculation for air

I have 1 litre of air in a sealed container at atmosphere pressure (approx 15 psi absolute). I want to reduce pressure in the container by 1 psi ( 14 psi absolute or -1 psig). If I understand ...
0
votes
1answer
27 views

Is 0.1 bar (hydrostatic pressure) equivalent to 0.1 bar vacuum pressure (absolute pressure)?

Suppose we would like to test the ability of an objec to withstand the pressure under 1 meter of whater. I would like to understand how to simulate this situation using vacuum. Is the 0.1 bar (for 1 ...
12
votes
4answers
2k views

Are there limits for the speed of sound? A maximum or a minimum only?

The speed of sound in materials of various states of matter differs a lot. But does it have fundamental limits? Is there a maximal possible speed of sound? Is there a minimal possible speed of ...
1
vote
3answers
46 views

Direction of pressure forces on a control volume (surface)

According to http://www.mne.psu.edu/cimbala/Learning/Fluid/Pressure/pressure_basics.htm, "Pressure always acts inward normal to any surface (even imaginary surfaces as in a control volume).". ...
0
votes
1answer
173 views

How to calculate fluid(oil / hydrocarbon) loss under pressure

I'm trying to calculate the amount of fluid that would flow through an area dependant on the amount of pressure that there is. I'd also like to know the rate at which it would flow. Essentially I ...
0
votes
0answers
15 views

Density and pressure of the earth core [duplicate]

According to some sources the density of the earth core is about 9.5kg / m^3 and the pressure: 4*10^11 Pa I know the gravitational force decreases, if you get closer the center of the earth, ...
6
votes
6answers
33k views

What is the difference between stress and pressure?

What is the difference between stress and pressure? Are there any intuitive examples that explain the difference between the two? How about an example of when pressure and stress are not equal?