# pressure's questions - Chinese 1answer

1.823 pressure questions.

### Physical meaning of same pressure on the same plan (hydrostatic paradox) with different weight above them

In this picture the points on red have the same pressure because the weight of the fluid is the same above them. But according to pascal law the point on black must have the same pressure(both 3 ...

### 1 Physical meaning of variation of force of pressure with altitude in fluid

We usually prove that pressure is a function altitute Z. Imagine a cube in a fluid, then the force of pressure on the bottom surface is higher than the force of pressure on the top surface. But we don'...

### Effect of mass on gas pressure

1 answers, 46 views mass pressure ideal-gas
I know that PV=nRT and this equation does not take mass into consideration. However P is also =Force/Area. And weight is a force which is equal to mg. Will gas pressure be dependent on the mass of ...

### Effect of volume changes on temperature in gases

1 answers, 14 views pressure temperature
If I decrease the volume of a certain container containing a gas; the KE of the particles will increase and therefore the temperature should increase. But according to Charles's law both of these are ...

### -1 Estimating the minimum hole size for leakage through a sealed membrane [duplicate]

Suppose I have a thin membrane sealed onto a flat surface along its perimeter, and there is water between the two surfaces with a certain pressure $P$. I would like to know, if I made a circular hole ...

### 5 Why do steam and hot water spray from my thermos flask?

3 answers, 1.301 views thermodynamics pressure
I put nearly boiling water in a Thermos flask (trade name for a vaccuum flask for home use). Later when I unscrew the stopper, steam and droplets of hot water are forcefully sprayed out, proving that ...

### -1 Pressure exerted by a liquid on the bottom of a submerged object [duplicate]

1 answers, 25 views pressure buoyancy
I understand that pressure increases with depth in a liquid and that it is the difference in pressures at the top and bottom of an object submerged in a liquid that provides the buoyant force. What I ...

### 6 Could the $Titanic$ have stayed afloat a bit longer if she kept moving, either in forward or reverse?

1 answers, 550 views fluid-dynamics water pressure flow
I was reading this question: Was Titanic's captain's decision correct? @oakad commented about a Russian vessel keeping itself afloat by going in reverse, using hydrodynamic pressure to keep ...

### 1 Drag calculation from pressure + shear stress distribution

0 answers, 20 views pressure drag stress-strain
If I know the shape of a body, pressure and shear stress distribution over it, how can I calculate the total drag acting on it ? More exactly, can I calculate it this way: Drag = [Pressure difference ...

### 2 Difference between pressure and temperature

If I am given the average kinetic energy of the molecules of a gas or a liquid, how can I tell if the fluid will burn me/crush me/both if I immerse my hand in it? Equivalently, what is the difference ...

### Does venturi effect violate pascal's law?

If we use Bernouill's law to compare pressure between point 1 and point 2, we find that P(2)gdH=0, we conclute P(2)=P(1). I must have made a mistake but where is?

### 1 What is the meaning of pressure in the Navier-Stokes equation?

2 answers, 91 views fluid-dynamics pressure navier-stokes
I have a hard time to wrap my head around pressure in the Navier-Stokes equation! It may sounds ridiculous but still I cannot understand the true meaning of pressure in the Navier-Stokes equation. Let'...

### 4 Why is the pressure same in a horizontal plane in a static fluid?

2 answers, 78 views pressure fluid-statics
One of the common explainations involve a cylindrical flask filled with fluid and Newton's second law. But such explainations is specific. What could be possible explanation in a case in which the ...

### -1 Breathing Air Underwater From A Car Tyre

4 answers, 1.038 views pressure everyday-life air biology
I've seen in many movies and programs the event where a car plummets off the road and in to a body of water, sinking rapidly. The car slowly fills with water as it sinks and the occupant(s) don't ...

### 1 Static Pressure in a Venturi vs a Free stream

We seem to have two conflicting measures of pressure in a Venturi siphon open to the atmosphere,$\hspace{100px}$. Bernoulli's principle says that, by energy conservation for a steady flow $Q$, the ...

### 1 Why is water inside a vacuum chamber not boiling?

1 answers, 60 views pressure water vacuum
I have a vacuum that shows a max vacuum gauge reading of 23"Hg when connected to a chamber. When placing room temperature water inside vacuum, the water doesn't boil. I have seen this chart before ...

### Is it possible to create circulation of water in bypass pipe without water pump?

There is a pipe of 32mm in diameter. Water flows from left to right. There are two branches in that pipe. To one of them connected input of water heat exchanger, to another - output of water heat ...

### 2 How to stop water flow in a siphon?

7 answers, 1.543 views fluid-dynamics pressure flow fluid-statics
I have assembled a small DIY drip-irrigation system for my terrace garden. Please have a look at the attached image. I switch on a small pump to start the drip-irrigation system and then switch it off....

### 2 How does the vertical distance beneath the surface of a fluid create pressure? (thought problem)

4 answers, 429 views pressure hydrostatics
Specifically, I am trying to wrap my head around this scenario but can't do so solely by thinking about the weight of the fluid. Imagine a perfectly still lake. If you dive into the lake, the ...

### Different types of mechanic jacks [closed]

I need help. I would like to know: what the differences between the jacks illustrated below are and with which jack a car can be lifted easiest (according to the answer sheet it is jack **B).** My ...

### -2 Physics/forces involved when separating two 5 gallon buckets

So a friend jokingly said "there's no force in the universe stronger than two 5 gallon buckets that are stick together." And I thought that this has to have a wonderfully complex and scientific ...

### 2 What is fluid pressure?

I cannot understand the concept of fluid pressure. Consider a liquid molecule at some point inside a liquid vessel. All the other molecules which are in contact with this molecule will exert normal ...

### Hydrostatic pressure in a gas

1 answers, 28 views pressure air fluid-statics gas
I have a physical picture of hydrostatic pressure ($dp/dh = \rho g$) in liquids, interpreting it as the weight of the water column. Now in a gas, the molecules are much further apart than in a liquid....

### 3 Trouble deriving hydrostatic pressure equation

I'm having a difficulty deriving hydrostatic pressure. To be specific, I don't understand this image from Wikipedia: How does the fluid below act on the below surface? Is it the normal force? Or ...

### 3 What happens to the pressure inside a tied-off balloon as the pressure outside the balloon decreases?

I'm almost 100% positive it would decrease, but my meteorology professor (who also teaches physics) says it will stay the same, because no air is escaping the balloon! Does the rubber of the balloon ...

### Bernoulli's equation: tube attached to a filled tank

I have the following problem where I need to apply Bernoulli's equation to find the velocity at the end of a tube that is attached to a hole of tank (filled with water), like it is illustrated in the ...

### Loudness of air movement

1 answers, 20 views forces fluid-dynamics pressure acoustics
Is the soundpressure, which is created by air movement, the same as if it is created by sounds? If you use a microphone with a pop filter and without a pop filter and you blow into it, than there is a ...

### 1 Do quantum fields with energy stored in it usually exert pressure?

There are types of quantum fields in the universe like spinor, vector, tensor, scalar fields. Do these fields with energy stored in it (as energy density) usually exert pressure, or be pressureless? ...

### Which density use for pascal's law for a cube emerged in a liquid

0 answers, 18 views fluid-dynamics pressure fluid-statics
If we consider a cube( with a density d) floating on a surface of a liquid( with a density d') and we want to evalute the difference of pressure between y1 and y2 (those 2 points are on the emerged ...

### Pressure generation due to opposing flows

1 answers, 198 views fluid-dynamics pressure flow navier-stokes
If two fluids are flowing at unequal velocities towards each other in a circular pipe, will a pressure be generated at the intersection? If yes, what will the direction of this pressure generated and ...

### Specific Volume vs Temperature Graph

2 answers, 51 views thermodynamics pressure temperature
When looking at a graph of comparing temperature and specific volume, we see that for increasing pressures, the boiling point increases and that the length of the saturated liquid-vapor line decreases....

### 1 How to understand air pressure against a hand pump?

1 answers, 20 views pressure vacuum air
Imagine this little though experiment with me for a moment. A piston sort-of contraption - like a bicycle pump, but without any nozzle to push air out of. One foot tall, one inch width/depth. Lets ...

### 35 Does car tire pressure change with weight of car load?

11 answers, 64.421 views everyday-life pressure
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, ...

### 2 How can pressure act in both the up and down direction?

It says in my textbook that pressure is a vector. So how does it act both in the up and down direction in the same body of water as seen in this image?

### 1 isothermal compression of water and definition of temperature

During isothermal compression of water vapor (below critical temperature), the pressure increases initially, and then remains constant up to certain point, and then steeply increases with small ...

### Biot coefficient as function of porosity

1 answers, 189 views pressure elasticity porous-media
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, ...

### Pressure of the same mass of fluids of different densities?

Suppose I have 2 fluids of different densities, and I pour the same mass of each fluid into 2 identical cups. I feel like I'm confusing myself here — on one hand hand, both cups contain the same mass ...

### 1 can I increase pressure with sound waves?

2 answers, 295 views pressure acoustics
I have a gas or a liquid in a container. Can I increase its pressure with sound waves or ultrasound or something? What I have in mind is that I can find the resonance frequency and make the molecules ...

### How to find velocity of water flow and $Q$ if I know static pressure at the end of the pipe of known diameter?

I have a pipe. At its end I have mounted pressure meter. Of course there is no circulation. Water pressure meter is a kind of stopper for water. I know diameter of the pipe, and I know its pressure in ...

### Using a Legendre transformation to convert enthalpy to internal energy

1 answers, 29 views thermodynamics pressure
Let us consider the enthalpy as a function of temperature and pressure, such that $H = H(T,p).$ Now, say we want to exchange the pressure $p$ by the volume $V$ by performing a Legendre transformation....