# Tag Info

7

This is not altogether correct. In particular, it does not matter what the pressure of the room is (unless you reach extreme values), because actually what is holding the water column is not some "high" value of the pressure at the bottom of it, it is the fact that the pressure at the top of the water column (at the water-finger interface, or in the air ...

6

That is right, deeper the pressure is stronger. But the pressure is not just in one direction it is in every direction. So the velocity will decrease in most cases. But also you have to be aware of the density of the object. You could read this classical description of diving objects "Thrust" on wikipedia. This is a classical effect, in real cases the ...

4

You are mistaken. Actually, you can melt ice by applying pressure. This is why ice is so slippery, when you step on a frozen lake, you are melting the very first layer of water, and thus creating a very good instant lubricant for you to slide on. It is a common knowledge false fact, see comments. Ok, granted, at very high pressures water does become solid. ...

4

While the capillary pressure in soil is many orders of magnitude lower than the atmospheric pressure, you also need to remember that in soil, the water is still in contact with the atmosphere, and thus is at atmospheric pressure plus capillary pressure. Since atmospheric pressure is orders of magnitude larger than capillary pressure, the pressure on the ...

4

Don't get too confused by the "bladeless fan" marketing babble. Something, probably a traditional blower, is pushing air around inside the device. This is ducted so that the flow blows in one direction from little nozzles on the inside of a ring. That causes a lot more air to be moved by Bernoulli's principle. Basically, the ring and nozzles converts ...

4

Pressure is defined as force per unit area applied to an object in a direction perpendicular to the surface. And naturally pressure can cause stress inside an object. Whereas stress is the property of the body under load and is related to the internal forces. It is defined as a reaction produced by the molecules of the body under some action which may ...

3

Let's assume a one litre $1000$ W electric kettle, filled with $0.5$ kilograms of water at $20^o$ C: It takes 4.2 joules to warm one gram of water one degree Celsius. So, to warm the $500$ grams of water $80$ degrees from $20$ to $100$ takes $168,000$ joules. The kettle will supply $1000$ joules per second, so it'll take $168$ seconds for the kettle to ...

3

Lets define some variables first. Lets say that the length of the column of air that you trap in the tube between the water level and your thumb is $h_0$ and it is initially at the same pressure as the surrounding air which we will call $P_0$. Lets also define the cross-sectional area of the tube to be $A$. As you draw the tube out of the water, the water ...

3

If You make a simplified force balance of a sinking box, You can identify two main forces: Force associated with box's weight $F_g$ acting downwards and buoyancy force $F_b$ acting upwards. The formulas are as follows: $F_g=mg$, $F_b=-\rho g V$, where $m$ is the mass of the box, $g$ is the gravitational acceleration, $\rho$ is the density of water, $V$ is ...

2

The answer to this question is quite intuitive when you think about what pressure is: a force per unit area. In a high pressure zone, particles experience a high force, and in a low pressure zone, they experience a lower force. The high force "overpowers" the lower force, pushing the particles from the high pressure zone to the lower pressure zone. You can ...

2

Yes - you can have a state where increasing the pressure would create a supercritical fluid See Phase Diagram

2

The difference between stress and pressure has to do with the difference between isotropic and anisotropic force. There's a Wikipedia section on the decomposition of the Cauchy stress $\boldsymbol{\sigma}$ into "hydrostatic" and "deviatoric" components, $$\boldsymbol{\sigma}=\mathbf{s}+p\mathbf{I}$$ where the pressure $p$ is ...

2

Contrary to the accepted answer: The gauge pressure, $P_{gauge}$ at a depth $H$ in a fluid of density $D$, where the acceleration of gravity is $g$, is given by:$$P_{gauge}=DgH$$ since the gauge pressure is the difference between the absolute pressure and the current atmospheric pressure. The absolute pressure is the gauge pressure, measured against ...

1

Hydroelectricity, used all over the world, creates energy from the pressure of water. Having made electricity, you can convert it to other kinds of energy. There does need to be motion-energy is force times distance. Just a static force does not give you energy.

1

Before the kink it had momentum density $\frac{\vec{p}}{V} = \frac{\rho V \vec{v} }{V} = \rho \vec{v_1}$; afterward $\rho \vec{v_2}$. The change in momentum density is $\rho (\vec{v_2} - \vec{v_1})$. Multiplying by $A v t$ (the volume that moves past the kink in time $t$), we get the change in momentum that must be supplied to maintain the kink (i.e. the ...

1

Maybe , depends on the temperature of the outside that it's hotter or cooler. If it does expands, you'll see that some water will drop off the tube . On the contary, if the air volume reduce , there might be some air at the end of the tube because water was vaccummed up by the reduction of air volume. Sorry for lots of grammar mistakes , I'm from Thailand. ...

1

Given a stress tensor $\mathbf{\sigma}$, which has 9 components in general, the pressure (in continuum mechanics at least) is defined as $P = 1/3 tr(\mathbf{\sigma})$. So the pressure at a point in the continuum is the average of the three normal stresses at the point. The off-diagonal terms manifest as shear stress. It's hard to say "stress" without ...

1

The reason is quite simple: the contents of our bodies (blood, bones, muscle, etc) are at the same pressure as the atmosphere. Even if they were not, atmospheric pressure is certainly not enough to get our bones crushed. When a diver is 10m under water, the pressure is doubled (202650 Pa). Any recreational diver can do that. I have been deeper than that, ...

1

The simplest reaction deuterium and tritium. Tritium is common in big labs (like NIF, JET, Omega) [1]. Tritium sucks - practically speaking. It is expensive, radioactive, and hard to stockpile. Omega spent millions and years on a tritium facility. It may even never be used in fusion power [2]. The next easiest reaction is deuterium with itself. This ...

1

The Wikipedia article answers most of your questions. What are the requirements for hydrogen atoms to go through fusion? Two atoms must overcome the coulomb barrier, which can be done by forcing two atoms very close together, or by leaving them moderately close for long periods of time, which allows them to tunnel through the barrier. Is it a ...

1

Yes, what you have formulated is fine. The pressure acting on the water from the bottom of the straw will be equal to the weight of the water times the cross section area. So $101325\pi r^2$ is the force acting from below also. That is precisely why there is an equilibrium and the water is not falling.

1

It is possible to create solid water with enough pressure. Water has other frozen state which do not contain the standard water crystal pattern. This is called amorphous ice. When we flash freeze organic food, the ice that forms does not conform to the traditional crystalline ice structure. The water does not expand, which prevents the cell walls form ...

1

This is a great question. I feel it necessary to point out the level of study and understanding that go behind asking this question. Well done! Here's the way I understand it. You analysis is flawless; in a radiation dominated universe, $a\propto\sqrt t$. That said, it is not correct to interpret this as the photons exerting some sort of pressure that ...

1

What you're missing is some practical aspects of modern plumbing. Every modern plumbing fixture(toilet, shower/sink drain) has a trap or "u-bend" in the piping before it connects to the sewer branch or main pipe. This allows a pocket of water to sit in the bend of the pipe to keep sewer gases from escaping back into the room when the fixture is not being ...

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