Force per unit area.

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3answers
14 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
12 views

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

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 ...
2
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2answers
80 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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3answers
861 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 ...
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0answers
12 views

Hydro electric energy transformation

Suppose you have a water source of 2L/s at a given altitude. Suppose you carry that water down to a reservoir 200m below. At that point you settle a hydro electric water turbine to convert the energy ...
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1answer
22 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 ...
2
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2answers
617 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 ...
4
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2answers
126 views

Water bombing - risks and possibilities

I just saw a video on youtube, where an excavator drops a load of water on a car, destroying it completely. I also saw a video with a fire-fighting plane dropping even more water on a burning truck. I ...
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1answer
40 views

How Much Weight Would This Put On The Legs Of A Desk? [on hold]

first time on this site and I need help with this, I got 2 stands 1 is longer and goes top of the other. The top of the stand will have 70 lbs on it and I want to know how much pressure (if that is ...
2
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1answer
47 views

Tornado Vortex Low-pressure Force

If a tornado forms not contacting the ground and then moves over a large flat roof and contacts that surface, producing low pressure above that surface and having normal, higher atmospheric pressure ...
1
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1answer
27 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 ...
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0answers
20 views

A block floating on water is pushed inside until it touches the bottom. Will the block come back? [duplicate]

A block floating on water contained in a vessel is pushed inside until it touches the bottom of the vessel and then released. Will the block come back? Bouyant force acts because the pressure on ...
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1answer
28 views

How can I apply a certain “pressure” (g/cm²) to the ground by dropping a weight?

I'm trying to find a way to apply 100g/cm² to the ground (substrate = snow) by dropping a weight from a particular height. If I drop 250g weight (80cm² area) from 1m, I'll get a velocity of 4.43m/s² ...
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1answer
95 views

How does force transmit through a solid block?

If you take a solid block, say, a cube of side length $l$ with density $\rho$, you place it upon a solid floor, and you apply an external pressure of $p(x,y)$ on the upper face ($x$ and $y$ define a ...
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1answer
66 views

How does the Moon influence atmospheric pressure?

I have just read in the Telegraph an article entitled Moon overhead makes rainfall lighter, scientists conclude. In that article there is the following statement: When the moon is overhead, its ...
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1answer
46 views

Velocity of water from a certain depth

I was curious to know does water come out of a certain depth when there is a difference in pressure, and also if it does come out of a certain depth, at what velocity does it travel at? So, ...
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2answers
145 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 ...
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1answer
62 views

Why doesn't a fluorescent lamp implode even though the pressure difference is very high?

According to Wikipedia, the pressure inside a fluorescent lamp is 0.3% of the atmospheric pressure, so the pressure difference between the outside and the inside of the lamp is almost equal to the ...
2
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1answer
110 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 ...
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2answers
2k views

How to model/simulate pressures and flows in a network of pipes

I'm having a hard time finding information on how to model/simulate this. I attached a couple files, both of which show an example tank & pump network. It's just nonsense that I made up for this ...
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2answers
852 views

Calculating pressure under water

Say I were calculating the pressure under 1 foot of water, in psi. I'm thinking the pressure is force per unit area, and should be equal to the force exerted by the column of water standing over ...
0
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0answers
15 views

Several suction pumps connected to same air flow source in parallel, is this set up unequal?

I have some sensors with built in vacuum pumps that are open to the room exhaust. I have a single sample source (a compressed air tank, connected to a T fitting and I side stream sample from one of ...
0
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1answer
31 views

Is flow speed between two pressures dependent on absolute or relative pressure difference?

Imagine you have a pressure chamber which is divided by a removable wall in two equal parts. Scenario A) Air pressure on the left side is 1 bar, on the right side it is 2 bar. Scenario B) Air ...
2
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3answers
370 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 ...
-2
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1answer
72 views

Boeing 737 Homework Problem [closed]

I have done the above problem, but have come out with a rather large surface area. Could someone point out my mistake(s)? Given/Assumptions: I assume $\sum F_y=0$ because it's level and straight. ...
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2answers
13 views

Gravity acceleration and hydrostatic pressure

I know that hydrostatic pressure $P$ is directly proportional to density $\rho$ and depth $h$. Why does $P$ depend on gravitational acceleration $g$ ? $P=\rho g h$ Is it because the force of the ...
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0answers
18 views

Minimum amount of water to pressurize pressure cooker

What is the minimum amount of water to create enough steam to pressurize a 6qt electric pressure cooker to 11psi( above atmospheric pressure) ? I am not wanting the recommended volume of water to ...
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10answers
20k 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
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2answers
35 views

How does the pressure inside car tyre change once the car is lifted/ put back on the ground? [duplicate]

Imagine a car on a jack; how does the pressure change once the car is lifted (all wheels in air - not touching the ground). I'd be interested in knowing whether the pressure will increase or decrease ...
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1answer
112 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 ...
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0answers
15 views

after pressure cooker is removed from heat-source

What happens inside a pressure cooker after it is removed from the heat-source and before the lid opens with atmospheric pressure? Specifically, what happens to the boiling point of the liquid(say) ...
3
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2answers
38 views

How do the Americas Cup Yachts sails work?

With the vast majority of sailing boats its pretty evident how the sails work to harness the energy of the wind to propel themselves forward. However on the modern Americas cup foiling yachts i can't ...
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1answer
28 views

How to calculate the pressure inside hose subjected to weight? (Example)

Example: Suppose we have a garden hose laid on a concrete floor. This garden hose is made out of rubber and is sealed on both sides. It is completely filled with water with no air bubbles whatsoever. ...
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1answer
45 views

Determining intake pressure of a cannula returning blood to an ECMO circuit

What are we trying to figure out: We want to know if it is possible to determine the pressure of the inlet for the catheter that returns deoxygenated blood to the ECMO system to help prevent ...
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2answers
105 views

physical meaning of pressure derivatives

Is there any physical meaning of the first and second derivatives of pressure with respect to time? If this helps, I am considering ideal gases.
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4answers
4k views

Why does sound need air in order to travel?

I know that in space, because of vacuum that we can't hear voices or sound to be specific, why is that? Why does sound need a medium to go through?
3
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3answers
97 views

How does pressure cooker work?

If you increase the pressure, the boiling temperature increases as well. In the other direction: if you decrease the pressure enough you could even make water boil at 18 dergees C. However I met this ...
3
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2answers
96 views

Can I cook an egg by holding it in thermosphere?

It is known that in thermosphere, air temperature is rising sharply with increase of altitude. In upper atmosphere, temperatures can even reach 2000°C or higher: see 2. However, air there is ...
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3answers
331 views

Can I blow soap bubbles (of air) inside a vacuum chamber?

When I blow soap bubbles from a liquid dish soap mixed with distilled water at atmospheric pressure at ground level both internal and external air pressure nullify and the tension of the bubbles ...
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3answers
927 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?
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1answer
40 views

Understanding the relation between pressure, ideal gas and, volume

I was given the following formula which is used for ideal gasses: $$pV = nRT$$ where: p:pressure V: volume n: number of moles R: gasconstant T: temperature now when speaking about vaporpressure ...
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0answers
26 views

How much pressure is need to lift tiles against gravity?

Vitrified tiles of size 600 mm by 600 mm and weighing about 7.5 kg each were laid with cement on floor of a building about a year ago. Building has glasses all around and premises are not occupied. I ...
2
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1answer
51 views

Are low pressure and high pressure areas responsible for rain?

My understanding is that low pressure areas are susceptible to rain. However, high pressure areas have no rain. Now, I want to correlate this with the following areas - Lower Hutt, Wellington , NZ - ...
1
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1answer
854 views

A water balloon in vacuum: does it boil?

If I put water in a vacuum it will boil. But what if I put this water inside a balloon ? I searched for answers and fount this video: http://www.youtube.com/watch?v=9q8F3ClUuV0 It seams that the ...
3
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1answer
35 views

Does a trumpet play at a tritone lower without lip vibration?

My trumpet teacher noticed that if you blow into a trumpet for warm-up, without any lip vibration, there is still a slightly audible pitch which is a tritone lower than "expected" in the following ...
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3answers
177 views

Question Regarding torricelli's theorem/Law

I recently studied about bernoulli's equation/principle. After the derivation of the said equation , my book gave some applications of the principle, which include torricelli's theorem/law. In ...
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1answer
9 views

Biot coefficient as function of porosity

Can the Biot poroelasticity coefficient $\alpha$ be approximated as a function solely of porosity $\phi$, and if so then how (and under what conditions)? I've read (e.g. 2.02-3 here) that it can, ...
23
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17answers
8k views

Doesn't a box holding a vacuum weigh the same as a box full of air?

This was recently brought up, and I haven't been able to conclude a solid answer. Let's say we have two identical boxes (A and ...
2
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1answer
166 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), ...
3
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0answers
22 views

Pressure inside a typical white dwarf

Does any one know the order of magnitude of pressure inside a typical white dwarf (better with reference)? Thanks! I think it should be $m_e^4c^5/h^3$ (may be multiplied by $\pi$), which is $10^{22} ...