Force per unit area.

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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
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2answers
238 views

Why is a hole in a ball?

I wanted to know why there is a hole in the ball (basketball, volleyball, handball) to fill the ball with air. Why can't the ball come with filled in air and fully sealed so that there is no loss of ...
5
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1answer
4k views

If 1 screw can support 120 lbs, how much weight can 25 screws support?

While this is mainly about my personal home improvement project, I figure this would be a good opportunity for some of you to apply your physics skills to a real-world situation. My situation is ...
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1answer
1k views

Area under a $pV$ diagram

What does the area under a Pressure volume diagram equal? I read in my textbook it equals 'external' work done, but why is this? First of all, what exactly is external work? Can you get it ...
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2answers
1k views

Jupiter Core is Solid Hydrogen

I was watching a show on the science channel about gas giants; there is something I do not understand. I am not a scientist, so this may be obvious to some. I learned that there a three states of an ...
3
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1answer
784 views

Does the magnitude of pressure on the sides (not the top and bottom) of a volume depend on depth?

I understand that at a point in a fluid, such as water, the fluid will be in equilibrium as the sum of the pressure from all directions will equal to zero. For a volume of water, the reasoning should ...
5
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2answers
14k views

Why does the balloon pop?

When we pierce a balloon with a sharp needle, it pops and produce a great sound. But, It doesn't pop when we open the mouth of the balloon (through which we have blown air)... So, Why doesn't the gas ...
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2answers
178 views

What is the pressure on an empty pneumatic tube?

At the residence I'm constructing a kitchen digester. The gas is to be collected into an old bicycle/scooter tube - initially as empty as may be after wringing it out.. Will the digester (total ...
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2answers
314 views

Opposing forces on an air cylinder — half force each or full force each?

If an air cylinder is pushing two platens apart with a force of $100\: \mathrm{lbs}$, do the platens need to push back at $100\: \mathrm{lbs}$ or $50\: \mathrm{lbs}$ each to keep the cylinder from ...
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2answers
1k views

Will the siphoning effect help a system pump water upwards if the water's entry and exit points are at the same height?

I am looking to pump water from a pool up to a roof for solar heating (black plastic tubing) and then back into the pool with the original source water. Does the gravitational force of the water ...
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1answer
285 views

How can I estimate relative humidity ($e/e_s$) from temperature and dewpoint?

Background my goal is to estimate vapor pressure deficit ($vpd$) from Relative Humidity ($rh = \frac{e}{e_s}$): $$vpd = \frac{100 - \frac{e}{e_s}}{100} e_s$$ (from Hartmann "Global Physical ...
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2answers
818 views

Necessary air pressure in flexible vessel to lift a certain mass

I have the following situation in mind: A big airtight bag of arbitrary shape with a person standing on it. The bag gets inflated with air to lift the person. Assuming that the bag is much larger ...
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1answer
3k views

Relationship between balloon size and pressure

I see numerous websites talking about how a small balloon is at higher pressure than a big balloon. This is a fun counter-intuitive factoid... unless it isn't a fact at all. Young-Laplace gives $$T ...
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1answer
2k views

Flow of momentum is pressure

In the diagonal terms of the energy-momentum tensor, the flow of $x$-momentum in the $x$-direction is the $x$-pressure. Why the flow of momentum is pressure?
3
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1answer
388 views

Which heated, partially filled bottle will explode first?

This is in reference to a pasteurization discussion on a homebrewing forum. I have four closed bottles which will explode if containing too much pressure. Two of them are 50% full (A and B), and two ...
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1answer
11k 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?
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1answer
599 views

Pascal law with two connected cylinders filled with water, and 50kg stones at both their ends

If I have two connected cylinders filled with water, and 50kg stones at both their ends (pressing both ends of the water) how much weight do I need to add on one side so that one of the stones reach ...
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2answers
5k views

Ideal gas law, pressure increase and temperature

If I had a container, full with air, and I suddenly decreased the volume of the container, forcing the air into a smaller volume, will it be considered as compression, will it result in an increase in ...
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3answers
325 views

Water, can it break through temperature?

If water is heaten up to ridicilously high temperatures, is it possible for the atoms in the molecules to lose their bonds? And if it is possible, isn't this some kind of chain-reaction? Like you ...
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1answer
2k views

How thick does steel have to be to be able to withstand 300 bar (sphere)

How thick does the material in a sphere have to be to withstand the (inner)pressure of 300 bar if the material is steel? (With an inner-radius of 2cm) Atmosphere pressure = same as 0 meter above sea ...
2
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1answer
151 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), ...
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1answer
68 views

Pressure change due to fan removing air from a non-airtight room

The following problem occurred to me today: Suppose a $100\mathrm{cfm}$ fan is pushing air out of a large room which is airtight except for a $10 \mathrm{cm}^2$ hole. The air pressure outside the ...
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2answers
185 views

Height of the atmosphere - conflicting answers

Okay. I have two ways of working out the height of the atmosphere from pressure, and they give different answers. Could someone please explain which one is wrong and why? (assuming the density is ...
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1answer
4k views

Calculate mass of air in a tyre from pressure

How can one calculate the mass of air inside a tyre, given a particular tyre size; a pressure, in $kPa = \frac{1000kg}{m\cdot s^2}$; and assuming room temperature, and normal air composition? I can't ...
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1answer
779 views

Gas Cylinder Life

Say I have a gas cylinder filled with nitrogen to some volume at some pressure. On that cylinder I have a regulator so that I get a steady pressure out. I wish to discharge the cylinder. How many ...
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3answers
1k views

Units of Distance, Pressure, and Temperature [closed]

I need to store data. I'd like to store them in Metric units and use a tool to convert them to and from other units that these data points will be displayed in. As the title states, my constraints ...
2
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1answer
174 views

Is it possible to use a powder-based firearm in space?

A firearm relies upon some kind of explosive powder to drive the slug out of the barrel. My guess however is that in space (at GEO, or higher) a firearm would be unusable due to the extremes of ...
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1answer
625 views

Basic Concepts of Water Pressure for Plumbers

I am learning how to install water pipes and I was told that to check if a pipe is leaking water I need to check the water pressure. But I don't understanding how water pressure works inside the ...
5
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1answer
2k views

Why is pressure in a liquid the same in all directions?

I'd like answers both in the more intuitive side an on the more precise side. Thinking of water as "cubes" of water, for example, would allow pressure in the z axis to be independent of the y or x ...
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1answer
424 views

How would this rapid depressurization of water really behave?

An in-development game(Starbound) recently released a demo of their water physics. At about 39 seconds into the video, a volume of water in a container is released when the cap on the container is ...
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2answers
831 views

How is energy transferred from one incompressible fluid to another?

When you apply pressure to an incompressible fluid the pressure is transferred. If you stop applying the pressure there is no motion. Volume and density are integral parts of calculating how much ...
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2answers
3k views

How can sound waves propagate through air?

We know that the sound waves propagate through air, and it can't travel through vacuum. so the thing that help it doing that is the air's molecules pressure. So my question how can that happens? I ...
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1answer
206 views

Is there a way to measure atmosperic pressure without an instrument?

Just that . I am not too much concerned about the accuracy of measurements .
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3answers
5k 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, ...
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6answers
11k views

Why does a gas inside a closed container experience atmosperic pressure when the gas itself is not in contact with the atmosphere?

I know this is a very basic (and probably stupid) question, but I have been confused about this for a long time.
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4answers
697 views

Water to ice expansion in $1\textrm{mm}^3$ pit - pressure on the pit walls?

[EDITED] by mistake, the subject was regarding 1m^3 instead of 1mm^3. There should be a significant difference between the two... A 1x1x1mm pit filled with water is frozen at a slow rate (1K/minute). ...
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1answer
2k views

Heat of vaporization of water - dependence on relative humidity?

Does the heat of vaporization of water depend strongly on the relative humidity of the gas into which it evaporates? Some context: If we want to calculate the dew point of water, we find the ...
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1answer
499 views

How is external pressure transmitted when a fluid is not enclosed?

Pascal's principle states that pressure applied to an enclosed fluid is transmitted undiminished to every part of the fluid. How is the pressure transmitted in the case where the fluid is not ...
2
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2answers
272 views

If I lift a submerged hose over 35 feet above the water's surface, what's in the top foot?

I've been arguing with a friend about the whole "perfect vacuum" concept. He and I agree that the most powerful vacuum pump in the world couldn't pump water more than ~34 feet above the surface of a ...
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2answers
7k 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 ...
4
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2answers
2k views

Electrostatic Pressure Concept

There was a Question bothering me. I tried solving it But couldn't So I finally went up to my teacher asked him for help . He told me that there was a formula for Electrostatic pressure ...
4
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1answer
2k views

What is the meaning of pressure of a solid?

Currently I'm taking an introductory course on thermodynamics. I've got a problem with understanding what is the meaning of pressure of a solid body. The question arose when I looked at phase diagram ...
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1answer
325 views

What could I test for in a guillotine? [closed]

I'm doing a school assignment project and I need to investigate something of my choice. I was thinking of doing something about how the height and angle the blade of a guillotine is dropped from ...
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3answers
52k views

Relation between water flow and pressure

Is there any equation that states the relation between pressure and water flow. I.e. Let's say that in 1 hour with 8mca (water collum meters) pressure I obtain 50m3. What if (giving the same ...
6
votes
1answer
202 views

What is the cause of noise generation at my bike helmet

I am looking for anexplanation of this phenomenon: I was riding my bike, (not driving it, was sitting on the back seat) with the helmet on. While the glass of the helmet was intact, I could hear ...
3
votes
1answer
346 views

Why does the bubbling of a soda bottle pulsate?

If I take a bottle of carbonated water and open the cap slightly to allow the gas to escape, there will be a sudden rush of bubbles foaming to the top of the liquid for a few seconds, then a partial ...
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2answers
941 views

Why does the higher pressure of air underneath an aeroplane wing keep it flying?

With aeroplane flight, the wings are shaped so that the air that goes over the top of the wing has to travel faster than the air that goes below the wing. This means that the air below the wing has ...
4
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3answers
2k views

Why is there a 90˚ phase angle between particle velocity and sound pressure in spherical waves?

My text says that in a plane sound wave (or in the far field), particle velocity and pressure is in phase. As we move closer to the sound source (to near field and more spherical waves), the phase ...
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6answers
28k views

Why are volume and pressure inversely proportional to each other?

It makes sense, that if you have a balloon and press it down with your hands, the volume will decrease and the pressure will increase. This confirms Boyle's Law, $ pV=k=nRT $. But what if the ...
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2answers
2k views

Why the pressure of atmosphere doesn't crush you when you e.g. walk outside?

Why the pressure of atmosphere doesn't crush you when you e.g. walk outside? I mean the density of air is $1.26 kg/m^3$, so with $100 km$ above us, it exerts much pressure on you when you walk ...