Force per unit area.

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9
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3answers
5k views

What about negative Pressure?

Here is something I see : Let's say the ideal fluid(water here) of density $\rho$ is drawn from a source by a motor and thrown upwards with a velocity $v$. Now we take the power of motor be ...
1
vote
2answers
80 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
26 views

The significance of the pressure term within the momentum-energy tensor [duplicate]

EDIT: this question is based around my notion regarding the possible role of potential energy in the momentum energy tensor T$_{\mu\nu}$, The answer below resolves the question and I have deleted ...
2
votes
0answers
19 views

Fluid flowing into small pores

I have some open porous foams with pore sizes ranging from 50-100nm. I want to flow water into this structure but even at 30 atmospheres it would NOT go in. I am looking for a way to calculate the ...
-1
votes
1answer
18 views

air pressure in elevator [on hold]

An elevator is accelerating upward. 1-How will the air pressure(P0) change? Will it decrease, increase or it doesn't change? WHY? 3- How will the formula of pressure(P=pgh+P0) change? 4- If a ...
0
votes
1answer
21 views

Balloon aerodynamics

In this recent anime that I have seen, there is a part where an atomic bomb is sent to the stratosphere in a box, by a helium balloon. As you can see in this picture of the set-up, there is a tube ...
0
votes
1answer
3k views

Determine the maximum height a pump can suck up water

I am working on a homework problem that presents the scenario of trying to raise water from a small reservoir of depth 8 m whose surface is 25 m below a pump that can maintain a pressure differential ...
2
votes
1answer
7k views

Best way to solve P-V-T Question

Typically in an exam or problem set we have a problem that's like this: Determine the specified property at the indicated state of water. Locate the state on a sketch of the T-v and P-v diagram. p= 3 ...
0
votes
1answer
162 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
1answer
45 views

How to get the pressure amplitude at any spatial point?

Working on the pressure equation from the linearized euler equations, I stumble across a very simple problem : How, from the pressure solution of the specific equation (see ...
0
votes
1answer
43 views

Finding volume of water that emerges from opening per unit time [closed]

A rectangular opening (width w and height h2-h1) is cut into the side of an open tank. The water doesn't emerge in a uniform velocity. Assume that SA of tank >> area of opening. I'm trying to study ...
1
vote
1answer
41 views

What is the pressure at the center of the Earth? (Or a neutron star)

The center of the Earth has microgravity and is thought to be solid and almost 6000 degrees hot. What is the pressure like there? The confusing thing, for the common man I suppose, is that there's no ...
1
vote
3answers
3k 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 ...
1
vote
1answer
20 views

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

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 ...
24
votes
11answers
9k views

Does car tire pressure change with weight of car load?

Does tire pressure measured by a meter on tire gauge change with load? (I am not interested in pressure produced by car tires onto the road). Car spec usually says "inflate to 220kPa normal load, ...
1
vote
0answers
21 views

Internal pipe flow - Pressure Drop

Let's say I have internal flow at some flow rate in a pipe that is 10 ft long and there are 2 straight sections and 2 bends. I am trying to determine pressure drop due to friction in the pipe. My ...
2
votes
1answer
149 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
33 views

Does spin degeneracy affect ideal Fermi gases in any way as T->Infinity?

In other words, given any system comprised of an ideal Fermi gas, in the high-temperature (classical) limit, are there any observable thermodynamic quantities (pressure, volume, energy, density, etc.) ...
1
vote
1answer
26 views

Static pressure in ducts and its dependency on speed flow and density

I know that depending on the duct circuit (bends, complex geometries...etc), the static pressure will be defined. If we assume air is flowing in the circuit with varying speed and/or varying density. ...
2
votes
2answers
31 views

Why is the temperature of the ice/water bath not dependent on the barometer pressure, as was the temperature of the boiling-water bath?

Part of a laboratory experiment question set. Why is it that the known temperature of the boiling bath can be accurately determined from the days atmospheric pressure but the atmospheric pressure is ...
5
votes
2answers
271 views

How come a whistling kettle starts whistling only when water boils, and not long before - due to hot air escaping under pressure?

A whistling kettle will start to whistle when the water boils and turns into a jet of steam which then exits the small aperture in the spout. But why doesn't this happen much earlier - when the air ...
1
vote
1answer
32 views

Deriving pressure from a given partition function

If the partition function for some system is given as $e^{\text{$\alpha $T}^3V}$; please note note that $\alpha$ is a constant. I have computed $$\left[\frac{\text{$\delta $Z}}{\text{$\delta ...
3
votes
3answers
172 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, ...
1
vote
1answer
28 views

what force pump is needed to power [closed]

Im studying design have not got a good grasp on maths, but understand the working principles of pressure and water! my problem hopefully has included all necessary info in the image. Please help. ...
0
votes
0answers
12 views

The contact pressure on a solid surface by a rod connected to a solid piston?

Below I have two pictures, one of which is single piston (blue) made of a solid material inside of a chamber (black) and the rod (magenta) is in contact with a rigid surface (teal). The second picture ...
0
votes
2answers
92 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 ...
0
votes
1answer
702 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 $2\times10^{-5}$ ...
1
vote
2answers
113 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 ...
0
votes
1answer
23 views

Pressure and force of ideal gas in a leaking container?

Let's imagine you have a container that has a pressure of 10 Pascals inside and a vacuum outside. The container has a volume of a cubic meter and I'm not sure if the temperature matters but lets say ...
3
votes
1answer
135 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 ...
2
votes
1answer
43 views

How does a hovercraft hover, if it has low pressure underneath it?

I've read a few different explanations of how hovercrafts hover, and they all mention a low-pressure cushion of air. This confuses me though: If there is low pressure under the hovercraft, why doesn't ...
4
votes
1answer
179 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 ...
0
votes
1answer
53 views

Why does Bernoulli's principle work?

So, if we have a large pipe which is constricted in the middle, the fluid in the middle section will move faster. Why is it so? What dictates that liquid that an X amount of it must pass on the other ...
-1
votes
1answer
566 views

How much pressure is needed to break an egg if applied from top and bottom?

Everybody knows that you can't break an egg with our fingers when pushing from top and bottom. I assume if we could squeeze hard enough the egg would break?
1
vote
1answer
45 views

Determining the components of the force on a curved surface due to pressure

I have a cross section of a half-tube with a pressure gradient across it causing a force outwards. I am attempting to extract the vertical component (in relation to diagram) of the force on this ...
0
votes
1answer
87 views

How the tube of a tire get puncture?

How the tube of a tire(cycle) get puncture? I mean, the inner tube is protected by an outer tube, so how is it possible to make a hole in the inner tube? And in general the puncture hole is very ...
2
votes
1answer
57 views

why does the temperature of spray cans always feel cooler than the temperature of the environment? [duplicate]

I know why sprayed gas is cooler due to evaporation thru different pressures, but I can't understand why is the can temperature always lower than environment?
1
vote
4answers
986 views

When pressure is exerted on parallel hydraulic pistons, do they start extending at the same time?

If there are two hydraulic cylinders connected in parallel, each with a different load (shown in the picture below), will they start extending at the same time? I'm having a disagreement with my ...
2
votes
3answers
10k views

About an upside down cup of water against atmosphere pressure

There is an experiment we learned from high school that demonstrated how atmosphere pressure worked. Fill a cup of water and put a cardboard on top of it, then turn it upside-down, the water will not ...
1
vote
2answers
45 views

How to calculate radius of a sphere of Ideal gas?

The problem I am faced with is approximating the mass of the sun, and I thought that a fancy approach would be to approximate the sun as being made up entirely of hydrogen atoms, finding the resulting ...
0
votes
1answer
10 views

How do I find out the excess pressure of the gas supply?

I have to find out the value of the excess pressure of the gas supply in a manometer. I'm not sure how to do this so it would be great is someone could help me. I also have to write my answer in ...
11
votes
2answers
154 views

How quickly should a fluid come to hydrostatic equilibrium?

Let's say I'm holding a one-liter water bottle, full of water, which I then drop. Before dropping the water bottle, the equilibrium is for there to be a pressure gradient in the water canceling the ...
1
vote
2answers
70 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 ...
2
votes
1answer
25 views

Relationship of the volume of a plumbing system to pressure

How does the volume of water a plumbing system holds vary with water pressure? I know the ratio would include the modulus of elasticity of the plumbing material, the total surface area of the plumbing ...
1
vote
3answers
30 views

Does atmosphere pressure affect the reading of a submerged barometer?

Suppose that: Temperature is stable. Atmosphere pressure at mean sea level is 1013hpa. I have a water proof barometer. Would the barometer reading be different between the following two scenarios? ...
1
vote
1answer
41 views

Will this balloon rise?

A helium balloon contains mostly helium which is an inert gas that is less dense than the air around it, suppose I drained all the air molecules from the balloon and note that this special balloon can ...
0
votes
1answer
69 views

Why doesn't atmospheric pressure crush thick walled structures?

There is one thing that puzzles me: common explanation of why don't structures collapse under the enormous atmospheric pressure (~101300N/m^2) is that the force pushing from inside balances out the ...
1
vote
1answer
32 views

How to derive velocity pressure in English units?

I know that velocity pressure can be calculated from dynamic pressure according to the potential energy of pressure (from Bernoulli's equation): $$ P = \frac{1}{2} \rho \overline{V}^2 $$ where P = ...
0
votes
1answer
45 views

Why does plugging a hole in an airplane's fuselage result in a huge (10x) atmospheric pressure spike?

While reading about uncontrolled decompression, I came across one famous airline incident, Aloha Airlines Flight 243, where the article I was reading discussed a 1-square-foot hole created in the ...
0
votes
1answer
42 views

Why is the melting point of an object inversly proportional to pressure?

In my science book it is written that as the pressure increases the melting point of a solid decreases but i think that it is wrong as the pessure will make the molecules stick together instead of ...