# Tagged Questions

Force per unit area.

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### Bulk modulus of supercrtical air

For gaseous state air has bulk modulus of ~pressure, but what about bulk modulus values about the supercritical pressure treshold, are these still pretty much same as the pressure or does this ...
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### What is the difference between pressure in water droplet and that in an air bubble?

The question is at least supposed to be simple but yeah, I need some detailed answers. I have tried thinking about it in the lines of surface tension but it seems what is required of me is more than ...
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### In a flowing fluid, why the particles are gathering together under critic distance and separating above this distance?

In a flowing fluid has an inner pressure which gives it some abilities. So this fluid is flowing from narrow gates, the speed of flow is increasing while the pressure of fluid is decreasing. If we ...
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### Does the rate of pressure change matter when measuring the strength of a closed container?

If I had a container that could hold 100 psi, and I increased the pressure to 100 psi instantly would I cause any excess stress on the container, or would it not make a difference from doing it over ...
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### Pressure or confusion

We all know that pressure is force per unit area. for example we have a pressure of $5N/m^2$, so is the load of $5 N$ acts on the entire area or it acts just at a point i.e. is the load a point load ...
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### Pressure in a balloon as a function of its diameter [duplicate]

Premise #1: Balloon is a perfect sphere Premise #2: We add water in order to increase the diameter of the balloon Is there an equation allowing us to find the pressure in the balloon, as the diameter ...
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### Static fluid pressure does *not* depend on the shape, mass, or surface area of the liquid. Huh?

I came across this figure that I'm currently unable to accept. I've come up with a thought experiment. Please point out my error: Assume zero atmospheric pressure and no boundary effects of the ...
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### How many PSI is required to evacuate water from a tube?

I am building a boat lift which has five flotation tubes (8' long, 36" wide and 40" deep) that has a 4" hole on the bottom of the tube. On the top of the tube is a 1" hose that connects to an air ...
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### What height is atmospheric pressure half that at sea level?

$PV = NT$, where T is a constant $P = \rho g h$ but I don't think this equation can hold in this form as the density is most definitely not constant as we go up in the atmosphere $\rho = \frac{M}{V}$...
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### Related to pressure and force [closed]

If we made a thing like the one shown in the figure where the cross sectional areas of two piston heads are different and exposed to the same atmospheric pressure and the air between the piston heads ...
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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### Why is a network pattern (weaving pattern) stronger than a whole solid surface of the same material

For example badminton racquets and huts.
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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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 ...