Force per unit area.

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Is it possible to consider PV diagrams without the equations of state?

Suppose that we have the equations of state for a particular system, or equivalently, that we have the fundamental relation $S = S(U,V,N)$. If we want to write down a PV diagram it will be quite ...
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1answer
58 views

Density solver for ideal mixture of real gases

I am referring the paper on GERG-2008 equation of state. I am interested in calculating the properties of ideal mixtures of real gases. The GERG-2008 EOS is in Helmholtz free energy and hence the ...
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1answer
64 views

$P = h \rho g$ derivation

Here is a snapshot from my textbook : Here only three forces are calculated: The gravitational force The force due to the pressure $p$ on the bottom surface The force due to the pressure $p+\...
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64 views

In enthalpy, is PV the pressure energy?

In the case of a fluid, does the $PV$ contribution to the enthalpy correspond to the pressure energy in fluid mechanics? (Related: What is Pressure Energy?)
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278 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 ...
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1answer
60 views

Is the pressure-gradient force an entropic force?

A gas flows from an area of high pressure to an area of low pressure when there are no other forces preventing it. From a macrosopic perspective you have to infer that an underlying force is ...
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83 views

Pressure in a fluid

If a fluid is flowing along a vertical line with a constant velocity, will the pressure at every point be the same and irrespective of height?
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24 views

Affect of temperature and pressure on humidity

If the temperature outside is 0°C and the air is fully saturated, when I heat the air to 21°C without adding any water the relative humidity inside the house would be a very dry 25%. The dewpoint does ...
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1answer
77 views

How do pressured containers within pressured containers behave?

If a container could hold 60 PSI of pressure and was placed into a larger container with the same strength, could you fill the large container to 50 psi and the smaller one to 100 psi, creating only ...
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46 views

why doesn't water in a inverted tumbler with its mouth covered with a porus cloth fall down ?

Is it due to the greater external atmospheric pressure acting upwards on the molecules or due to surface tension ?
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1answer
34 views

general formula for water pressure

In a Sears & Zemansky Physics text, a general formula for fluid pressure is introduced. An infinitesimal element is created in the fluid with thickness $\mathrm dy$ and surface area $A$ at a ...
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1answer
63 views

Atmospheric pressure of Venus?

I have seen the calculations on the atmospheric pressure of Venus - 90 times that of earth. With gravity very similar to earth, how does Venus do that. The calculations I have seen assume constant ...
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2answers
98 views

Boyle's Law-$ PV= nRT.$ What equation should be used to find pressure if n is not constant, like in an elastic system?

When air is added to an elastic system, like a balloon, the volume and pressure change. Would use Boyle's Law- $PV=nRT,$ but n does not remain constant in this situation. Known: $V_1$ is at ...
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48 views

Definition of atmosphere unit and relation to temperature and gravity

I've seem sometimes the atmosphere unit for pressure be defined so that $1\ \mathrm{atm}$ would be the mean atmospheric pressure at sea level. I've seem on the other hand the following definition: ...
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1answer
54 views

Physics behind blowing soap bubbles

Is it possible, using the surface tension of a soap bubble, to calculate the maximum pressure (created by the air flow) it can withstand while still attached to the orifice to prevent it from bursting?...
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1answer
65 views

Is it possible to 'push' a path to the Earth's core?

This may very well be a question for Earth Science SE, but as it is very hypothetical, maybe pure physics is more appropriate... Question: Imagine we have have a wedge that tapers down into an ...
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1answer
69 views

Explaining the shape of a raindrop and a drop of mercury

I saw on wikipedia that the shape of a raindrop is explained by using Laplace pressure. But why? Since the drop is in motion, we shouldn't be able to use an hydrostatic law, am I wrong? ...
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1answer
59 views

Why a balloon explodes by itself? [duplicate]

I was wondering why a balloon explodes after some time by itself with no specific reason. yesterday I was doing my chores and to my amazement the balloon far in the corner of house pop with no obvious ...
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1answer
111 views

How do snails avoid being cut while crawling over a razor blade? [closed]

This YouTube video shows a snail crawling over the edge of a razor blade without being harmed. The author claims that: To us, slug and snail slime is gooey and gross but the mucus is one of ...
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47 views

What is the difference between the pressure and “pressure force”?

I am in the process of going through a question pertaining to inviscid flow over a cylinder. The velocity field is, in polar co-ordinates: $$\vec{u} = U_{\infty}(1 - (\frac{a}{r})^2\cos2\theta,- (\...
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2answers
117 views

Why does pressure decrease as velocity increases?

Bernoulli's principle states that as velocity increase pressure decreases. But higher the velocity, greater is the temperature and pressure must be high. Can you explain the situation in both the ...
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30 views

Pressure testing watch using common tools? [closed]

I want to test if my new watch complies with ISO 2281 (https://en.wikipedia.org/wiki/Water_Resistant_mark) That seems doable in the kitchen apart from 2 steps: Resistance to water overpressure. ...
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2answers
75 views

Why do we take $h$ as “height from surface to bottom” when calculating liquid pressure?

In the following image, pressures of points x, y and z are $P_{x}, P_{y}$ and $P_{z}$ respectively, and they all are equal. My question is, why? The amount of matter on x is much more than amount of ...
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3answers
77 views

Calculate acceleration based on differential pressures

In my example, water is in a tube and is being accelerated by a compressed air. I already know that $P = \frac{F}{A}$ so if you know the pressure and you know the surface area its acting on, you can ...
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13 views

How much pressure would be on Mars if the icecaps melted?

I was wondering, The martian polar ice caps are made of water and CO2. All documentaries say that melting the poles can add pressure. How much pressure would there be? I know that every summer they ...
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1answer
165 views

If my windows are open on a windy day, the curtains sway and the doors slam shut. Why don't I feel this wind?

I am standing indoors, right in front of my open window, as I see my curtains moving back and forth and I can hear my closed doors shaking. I can also hear the wind howling loudly. Why don't I feel ...
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2answers
22 views

Would a hybrid mixed medium balloon allow you to use less helium to lift equivalent weight?

Suppose you had two balloons, one inside the other (a inside b). Would filling balloon "a" with the 80% nitrogen/20% oxygen mix you find in the surrounding air at ground level, and then filling ...
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1answer
23 views

If there was an object such as a bucket travelling through the atmosphere very fast could the air caught in it transition to a liquid?

The question came to me after thinking of the pressure waves in front of a spacecraft during re-entry. Would the pressure caused by the air being compressed cause the air to liquefy and if so at what ...
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1answer
27 views

Why doesn't volume change account for the energy change in this problem?

Problem: A mass of 200 g of saturated liquid water is completely vaporized at a constant pressure of 100 kPa. Determine the amount of energy transferred to the water. My approach: Assuming change in ...
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2answers
69 views

Pressure Volume graphs and work done

So if I have a system where pressure, volume, and temperature change, how do I find the work done on the system? I look at an example where you simply use $\mathrm{d}W =-p\, \mathrm{d}V$, but I ...
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1answer
59 views

How does water height in a vacuum chamber effect pressure

I am testing for package leaks in non-porous packages. Quick details are: 1) Package is sealed at atmospheric pressure. There is some headspace inside the package which is just air. 2) A small hole is ...
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29 views

Pressure vessel analysis of transversely isotropic multilayer material

Suppose I have a transversely isotropic, hyperelastic material with known strain energy that is a fibrous composite. I am interested in an explicit formula for the displacements (so I can get the ...
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20 views

pipette waterfountain

Place the tip of a pipette in some hot water. Cover the other end with you thumb. Invert the pipette and water sprays out nearly two metres. Is the cool air in the pipette being heated by the hot ...
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2answers
94 views

How does the general relativity describe the pressure?

The general theory of relativity describes the gravity as a geometrical feature (in very twisted geometry). That's comprehensible to me when the motion occurs and "the most straight" trajectory is to ...
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0answers
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Measurements of the pressure drop across wind turbines?

Mathematical analyses of wind turbines show that a discontinuous pressure drop happens at the rotor plane. I am looking for measurements of this effect, but I could not find any. Do you know any (...
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136 views

relationship between pressure and thermal conductivity

Using a kinetic model for gases, is it possible to derive a relationship between pressure and thermal conductivity? From what I have read, I thought pressure was independent of thermal conductivity? ...
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1answer
31 views

speed distribution and mean free path of gases at pressure

I know that at 18,000 ft. above mean sea level, the atm. pressure ~half of what it is at seal level (760 Torr). The temperature also decreases by 70C. a. How would this change the speed distribution ...
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1answer
49 views

Would a Tesla Valve create a pressure differential?

Start with two sealed boxes that are the same in every way. Then connect them by a tesla valve so that air could flow between them. Over time through entropy would the one-way preferential flow of ...
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1answer
27 views

Force on sides of a pool [closed]

I am going to create a large pool of water for a stage production. The volume of water will be 6m x 5.2m x .15m deep. I want to check how much pressure or force will be exerted on the surrounding ...
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2answers
74 views

Difference between water and ethanol density for an object [closed]

I'm just slightly confused. Say that I had an object that floated 19.4m in water from the bottom of the object to the surface. Now I was going to change the fluid to ethanol, which has a density of ...
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1answer
83 views

Why is root mean square pressure used in the definition of sound pressure level?

I dont understand the way we measure loudness. I know that it is in some way related to the magnitude of pressure variations. please help me figure out where my understanding fails. Let $p(t)$ be the ...
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2answers
168 views

If I Blow smoke out my window, will any come inside my room?

My girlfriend and I have got into a lively debate about whether or not my flatmates can smell the smoke I blow out my window. Can you help us? Here is the scenario. The smoker, places himself ...
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1answer
31 views

How much force would an explosive decompression really provide?

In science fiction, explosive decompression is occasionally used to slow down or provide a nudge for very large spacecraft (for instance, recently in the 2015 movie The Martian, and in this old Star ...
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1answer
63 views

Velocity of water column

If an air filled tube 5 km long with a diameter of 20 m was submerged vertically under water one end 5 km underwater and the other end at the surface, how fast would the water column rise if the ends ...
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3answers
34 views

Pressure and altitude

I am going to ask a simple question, for sure. The pressure with respect to the altitude is given by this formula Where sea level standard atmospheric pressure p0 = 101325 Pa sea level standard ...
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1answer
22 views

Does moving air suck in air from left and right of its path? [closed]

When air is made to move (e.g. by a fan) it has a lower pressure than when it is still. Essentially, this moving air should become a low pressure zone relative to the static air around it and the ...
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2answers
102 views

Gravitational Wave Impact

What would we see and feel if the waves were powerful enough? Do the waves influence whatever they pass through like a pressure wave would? Or would they be more transparent to the subject there ...
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1answer
43 views

How do buoyancy control devices (BCD) work?

I get that having more air decreases density and increases buoyancy. However, we can take the diver-BCD-oxygen-tank to be a single system. How can the pumping of air from the tank into a vest around ...
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1answer
48 views

Methods to solve a vapor pressure equilibrium question with water on the moon? [closed]

"Imagine a tall column of water on the Moon, maintained at a temperature of 50°C and left to the open vacuum at the top. Up to what depth will the water continue to boil? The Moon's radius is 0.273 ...