Force per unit area.

learn more… | top users | synonyms

0
votes
1answer
26 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? ...
8
votes
3answers
10k views

Why did my frozen water bottle explode when I opened it after it defrosted a bit?

Last night I filled a 20 fl oz bottle (http://www.thenibble.com/reviews/main/beverages/soft-drinks/boylans-mash.asp) with lukewarm water from my tap. I filled the bottle pretty much to the brim, ...
13
votes
5answers
18k views

If I take a bottle of air into space, and open it, where does it go?

It seems to me that space doesn't have any/much air, and if my bottle is full of air, when I open it, where does the air go?
8
votes
1answer
79 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 ...
5
votes
3answers
10k views

Pressure of sealed in liquid nitrogen

If you take a container of great strength, fill it to the brim with liquid nitrogen, seal the container, and heat it to room temperature. What will the pressure be inside? Bonus: The same with ...
11
votes
5answers
2k views

What would actually happen to a person jettisoned into space?

Alright, so we have all seen the movies where someone gets blasted out of the airlock on their starship, or their suit decompresses while on a space walk. The poor schmoe usually either decompresses ...
8
votes
1answer
265 views

What happened to this folded paper in a hydraulic press?

The video below apparently shows a man folding an A3 size piece of paper 7 times, putting it under the hydraulic press each time. After 7 folds, on the last press, the paper sort of explodes. What's ...
6
votes
2answers
170 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 ...
1
vote
0answers
26 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 ...
2
votes
2answers
183 views

Balancing forces on a liquid [closed]

My reasoning is as follows Atmospheric pressure = $P_{0}$; Spring stretch = $x$; Pressure under top piston = $P$ Balancing forces on top piston $kx + P S_1 = P_0 S_1$ Balancing forces on bottom ...
-4
votes
2answers
38 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
vote
0answers
20 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 ...
0
votes
3answers
2k views

Pressure change with a pipe diameter change

I have a question regarding a water line from the street to a house. What happens to the pressure in a water line if it goes from a 1" diameter pipe (at street) and increases to a 1.5" diameter pipe ...
7
votes
1answer
3k views

Does water turn solid under deep ocean because of high pressure?

I know that we can make water solid with high pressure, so I think water will be solid in the deep ocean? If that is true, the depth of the ocean would be limited because water will become ice? ...
2
votes
0answers
24 views

Ratio of Stagnation to Normal Flow Properties in Incompressible Flows

I know in compressible flows the ratio of stagnation to normal flow variables is a function of the Mach number and usually the specific heat ratio. Does this ratio mean anything for incompressible ...
2
votes
3answers
38 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
0answers
15 views

What is this “outgrowth” on air tube in tonometer? [closed]

I found the following "outgrowth" in air tube in electronic tonometer: The hole is apparently closed and air doesn't go out of it when tonometer pumps air inside. What is it for? Isn't it for ...
0
votes
1answer
22 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 ...
3
votes
2answers
71 views

Would an undersea reverse osmosis station work?

According to Wikipedia, saltwater reverse osmosis occurs at 600-1200 PSI. Saltwater adds .455 PSI per foot, so 900 PSI would be at a depth of about 1980 ft or 603 meters. This is about halfway ...
1
vote
3answers
38 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 ...
8
votes
2answers
112 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
2answers
33 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
56 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 ...
3
votes
1answer
24 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, ...
0
votes
4answers
124 views

Velocity of a leak in a closed water tank

Bernoulli's equation states $P_1+{1\over2}\rho v_1^2+\rho g h_1 = P_2+{1\over2}\rho v_2^2+\rho g h_2$ In a classic "water tank with an open top and a leak" scenario, "point 1" is the surface water ...
0
votes
3answers
2k views

Specific heat capacity at constant volume VS constant pressure

For an ideal gas, why is the specific heat capacity at constant volume lower than the specific heat capacity at constant pressure?
10
votes
5answers
9k 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 ...
2
votes
2answers
774 views

Dynamic water pressure from flow and diameter

I have 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 one. After Googling a lot, I found two formulas allowing to compute the ...
1
vote
2answers
167 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 ...
3
votes
0answers
37 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
27 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} = ...
0
votes
2answers
261 views

Pressure and humidity

Does pressure/vacuum affect water vapor differently than other gases and hence humidity? For example, imagine I have a vacuum bell at atmospheric (mean sea level) pressure and the air in it is 50% ...
1
vote
2answers
35 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: ...
0
votes
1answer
28 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
1answer
124 views

Why is it not possible to use the ideal gas law to determine if the pressure changed in this situation?

I was given this question for my homework: A cylinder with a valve at the bottom is filled with an ideal gas. The vale is now opened and some of the gas escapes slowly. The valve is then closed, ...
0
votes
1answer
49 views

How does pressure change over time in an open box?

Imagine that you have a 1 cubic meter metal box with two 20 mm diameter holes. One of them is connected to an air-compressor that constantly pressurizes the inside of cube. Let's say 5 atm. The other ...
0
votes
2answers
41 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
30 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: $F_o=pA_o=p4\pi (r+l)^2$ ...
0
votes
4answers
94 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 ...
3
votes
1answer
148 views

How to compute this change of Gibbs energy for a Van der Waals gas?

The change of Gibbs energy at constant temperature and species numbers, $\Delta G$, is given by an integral $\int_{p_1}^{p_2}V\,{\mathrm d}p$. For the ideal gas law $$p\,V=n\,RT,$$ this comes down to ...
0
votes
4answers
45 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 ...
1
vote
0answers
71 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 ...
1
vote
1answer
19k views

How much work is needed to compress a certain volume of gas?

I want to know the formula (and what does the symbols stand for) for how much work is needed to compress a certain volume of gas?
8
votes
4answers
3k 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 ...
0
votes
1answer
182 views

What is the physical fundamentals of Pascal's law

Pascal's law or the principle of transmission of fluid-pressure (also Pascal's Principle) is a principle in fluid mechanics that states that pressure exerted anywhere in a confined incompressible ...
0
votes
1answer
122 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 ...
0
votes
1answer
25 views

Why Nitrogen is still (almost) 3 times as abundant as Oxygen in Troposphere? [duplicate]

I learned that our atmosphere has ~78% Nitrogen and ~21% Oxygen. If I fill a glass with 21% water and 78% Canola Oil, the more dense (and thus heavier) water will take a full bottom later and Canola ...
1
vote
1answer
174 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), ...