Force per unit area.

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1answer
24 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.
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0answers
27 views

When does a balloon burst? [on hold]

I'm working on a project and I need to know something. and that's : When does a balloon burst? I mean, does it have any relation to its internal pressure or its volume? for example can we say a volume ...
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1answer
24 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 ...
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2answers
308 views

Existance of gusts of wind, an anamoly?

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 ...
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2answers
26 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?
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0answers
13 views

Can super heated air be used to drive a turbine driven engine? [on hold]

Air a mixture of gases is ever trying to expand. By accelerating this property can air be used as a fuel in a turbine driven engine which can give sufficient output to be used in an automobile.
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0answers
14 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 ...
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1answer
26 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 ...
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0answers
10 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 ...
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1answer
15 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 ...
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0answers
61 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 ...
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3answers
79 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 ...
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2answers
31 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 ...
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5answers
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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 ...
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0answers
20 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 ...
2
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1answer
75 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 ...
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3answers
45 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 ...
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0answers
14 views

Vertical pipe longer than 10m, full of water, top end closed, bottom end under water?

Normal surface air pressure is around 1 bar which is roughly the same pressure of a 10m water column. If I have a pipe full of water that is more than 10m long, top end closed, leave the bottom end ...
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1answer
23 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 ...
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1answer
29 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 ...
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1answer
26 views

What forces act on an object submerged in flowing fluid in an enclosed environment (i.e pipe)?

Let's say we have a pipe with water flowing through it and obstacle is inserted into the pipe and is rigidly fixed to the inner wall so that it does not get washed away. What forces are exerted by ...
2
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3answers
68 views

What is basically the difference between static pressure and dynamic pressure?

What is basically the difference between static pressure and dynamic pressure? While studying Bernoulli's theorem, I came before these terms. The law says: When the fluid flows through a small ...
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1answer
32 views

Pressure, Momentum and Energy: A 'Peculiar' Relation

Is the following possible? $$ P = \frac{p^2}{3E} $$ where $P$ is pressure, $p$ is momentum and $E$ is energy. In what convention is the above relation acceptable? EDIT: The source paper can be found ...
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0answers
11 views

What kind of carbon allotrope coating do I have to give to a plough to make it more efficient? [migrated]

So I have this situation; I am doing a school project on the usage of carbon allotropes instead of steel, but I recognized a problem: The much lighter weight, although stronger would have less ...
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1answer
49 views

Can I tell where a leak is in a vertical water pipe based on the water pressure at the bottom?

I have a buried water line with a leak in it and I want to locate approximately where it is. The line runs uphill to a storage tank. I've isolated the leak to one section of the pipe. The diameter of ...
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1answer
45 views

Decrease in system pressure do to gas dissolution?

A system of fixed volume contains two fluids as illustrated in the figure below, in equal volumes. Their pressures are both equal and high (much greater than atmospheric pressure). Initially the ...
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2answers
69 views

High Pressure Processing(HPP) of juices in a plastic bottle container

High Pressure Processing (HPP) is a cold pasteurization technique by which products, already sealed in its final package, are introduced into a vessel and subjected to a high level of isostatic ...
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1answer
337 views

Pressure and Tall Buildings

Does living in tall buildings somehow exert more pressure on our bodies? I remember reading something about this once but I'm not sure if its true.
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0answers
28 views

Why does opening the sun roof at high speeds cause the air pressure to change inside?

When I'm driving at fairly high speeds (80mph for example), I've noticed that opening / closing the sun roof causes the air pressure inside to shift significantly, a change that I feel clearly in my ...
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2answers
32 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 ...
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0answers
28 views

Lovely flow rate [duplicate]

How can we calculate the measure of the air flow rate when it is coming out of the balloon? (I mean that which parameter affects that? For example, the measure of balloons neck or the ratios or ...
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2answers
36 views

How can a small volume of gas balance the pressure exerted by the whole atmosphere?

Consider a balloon filled with Helium or even air for that matter. The membrane of the balloon is in equilibrium because the atmospheric pressure on it exerted by the atmosphere, the elastic force by ...
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1answer
33 views

The relation between Internal Pressure and flow rate in a balloon [duplicate]

I'm working on a project. We have two balloons, connected by a hose with a valve.We know when we open the valve, by according to internal pressure of each balloon, air goes form the higher pressure ...
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4answers
92 views

Relation between temperature and pressure?

I was just working on a special question but I ignored the effect of temperature on it and now it becomes very important to me. What is the relation between Pressure and Temperature? Suppose we ...
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1answer
32 views

Can covering an open container with a lid change the pressure of gas in the container?

Consider an open container at standard atmospheric pressure. Now a lid is placed over it, in the most normal way possible. Would the pressure of gas inside the container be the same as the standard ...
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0answers
28 views

What's the relation between the type (Gender) of a balloon and its internal pressure

I'm working on a project about balloons and I need to know the relation between the gender of the balloon and its internal pressure. As far as I know, there are some parameters such as " Elasticity of ...
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1answer
35 views

Mullins effect in the elastic material

I was thinking on a experimental question, but I couldn't get the answer: How can we measure how the Mullins effect influences in the pressure inside a balloon? (I mean that, if there is a formula, ...
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4answers
56 views

Can this container withstand a vacuum? [closed]

I am putting together a piece of equipment that will involve a vacuum pump pulling up to 10 Torr / 13 Mbar.  I need to use a container for liquid within the equipment and have found a stainless steel ...
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0answers
14 views

molecular explanation of pressure in water at depth

At 10 m under water, pressure is 2 atmospheres. As temperature is not different, and density is minimally different, how does pressure increase at the molecular level (collisions per unit area)?
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0answers
18 views

How do I calculate the speed of the air particles flowing out of a balloon? [duplicate]

I am trying to find out what kind of force would a leakage in a balloon cause. What i used is F = (mass flow)speed = (air density)(surface of leakage hole)*speed. I don't know how I could calculate ...
9
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6answers
1k views

Gay-Lussac's Law & the Patriots

This may be a question better suited for xkcd what if? section...but here goes: with all the hoopla around the patriots / colts game and allegations of cheating by deflating footballs, I've read/heard ...
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0answers
15 views

Pressure evolution equation atmosphere

Working on gravito-acoustic wave propagation in a windy and viscous atmosphere I tried to recover the pressure evolution equation. My starting point was the adiabatic state equation : ...
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1answer
21 views

When is it appropriate to drop pressure terms when applying conservation of momentum to a fluid?

I'm trying to wrap my head around pressure forces in incompressible, irrotational, invicid flow. Applying conservation of momentum to a control volume gives me \begin{equation} ...
0
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1answer
36 views

Fluids in a U-shaped Tube

One of the users asked a question about the Fluids in U-shaped Tube. I was wondering and I tried to imagine that the membrane is fixed and the left side is filled up until $h_1=h_2$. So my question is ...
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2answers
38 views

Fluids in U-shaped Tube

In a U-shaped tube, water and oil are separated by a movable membrane. What is the ratio of the heights $\frac{h1}{h2}$ (density of the oil $ρ_{oil}$ = 0.92 $\frac{g}{cm^3}$)? I tried solving by ...
3
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2answers
102 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, ...
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0answers
20 views

Opening of a Soda Bottle - Gas effects

Referencing the answer given here: Why does the bubbling of a soda bottle pulsate? I've noticed that when I open the cap a little and then close the cap, the walls of the plastic bottle harden ...
2
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1answer
64 views

Why I can't feel the difference of atmospheric pressure between a closed room and outside?

As far as I know atmospheric pressure is the result of the weight of earth's atmosphere. It has an approximate value of $10^5 Nm^{-2}$. Then why I can't feel it? My physics teacher told me that we are ...
9
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0answers
235 views

Definition of stress at the microscale

Take, for simplicity, a Lennard-Jones fluid below the critical temperature, which is to say that there is a phase separation into fluid and gas and thus an interface is formed. The macroscale picture ...
5
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1answer
365 views

Bowling Ball Sinking Rate - Variable or Constant?

In today's (Jan. 16, 2014) xkcd What If?, Randall Munroe discusses how fast a bowling ball will sink to the bottom of the Mariana Trench. He calculates the drag on the ball, and then plugging in the ...