# Tag Info

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The biggest, immediate problem with "openning the door" of a spacecraft is not that you would die immediately from exposure to the vacuum of space: you don't - you have of the order of minutes to do something about it. The problem is the violent outrush of air. User rob offers this answer to the Physics SE question Do airlocks in space decompress violently ...

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people in spaceships opening doors and closing them again with no suits on. Is it possible in "real life" No, it is not. Any sane engineer will build doors that open inward, or have latches that over-center when closed so it is simply impossible to open an airlock in a pressurized vessel. An aircraft, for example, has about 6-8 tons of pressure holding ...

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A reasonable sub woofer at sound power level of 130 dB would produce pressure fluctuations of 60 Pa. Compare this to the ambient pressure of 100'000 Pa and you will see that related temperature fluctuations would be negligible. It extinguishes fire because it pushes the air back and forth. For the small fire in this video you could take a small air blower ...

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Yes, there is a force, because the air pressure inside the tire is larger than the pressure outside, so air will try to leave from any hole it finds, however small. It might be through some micro cracks on the tire or, more often, through leaks from the air valve.

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The boiling point of any substance may be defined as 'the temperature at which the pressure of its own vapors become equal to the external pressure'. So for example in the case of water, at 100oC, the vapor pressure become equal to approx. 1 atm. Now if you increase the pressure further, you would need to heat the sample more such that the new pressure is ...

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You assume that the screen is perfectly absorbing when you use this field. By uses this field you are assuming that the electromagnetic field pass through the material without reflection. Furthermore, you are assuming that you don't have field in the another side of the surface. $$\textbf{E}=E_0e^{i(kx-\omega t+\delta)} \hat{\textbf{y}}, \ \ x<0$$ $$... 2 A gas (like air) will tend to diffuse through any material, and the rate of diffusion will be roughly proportional to the pressure difference between the inside and the outside. It so happens that it tends to diffuse through the rubber of ordinary bike inner tubes fairly rapidly. In addition, the inner tube wall is quite thin, and the thinner the material ... 2 Assuming the oxygen and lead vapour can be treated as ideal gases then yes the partial pressures of the two will be the same. This happens because the pressure is proportional to the momentum of the atoms multipled by their velocity (shout if you want me to explain why this is):$$\begin{align} P &\propto pv \\ &\propto mv \times v \\ ...

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Others have explained the physics. I just want to add that those of us with low body fat can become negatively buoyant at the surface if we breath out and empty our lungs. I can sink down and sit on the bottom of a swimming pool. So it is very possible to dive to a depth where you have negative buoyancy but what depth that will be will depend on the density ...

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I will focus on just a little bit of one of your questions - the relationship between compressibility, density and pressure - and per my comment, recommend that you narrow down the scope of your question. As you know, in a gas we experience "pressure" because molecules hit the walls of the containing vessel. When I double the number of molecules in the same ...

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You would have quite a problem to keep your water liquid. Normally, the water will evaporate when pumping. So you should go to low temperatures, but it freezes there. I thin you should thing about some other material to make bubbles in vacuum.

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Yes. When you do stress testing of materials (for example, the Brazilian test of a disk shaped test object) you apply stress along a single axis (using for example an Instron machine). This is a good way to measure elastic properties of materials. On the other hand if you have a pressurized container (for example the hydraulics in your car brake system), ...

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The joule Thompson coefficient is negative as the gas is coming out through the small hole, for negative coefficient the tempr. decreases and for positive coefficient the tempr. increases.

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'Negative ' pressure is strictly a relative state; relative to what one may wish to define as zero pressure, and here on earth we chose to define that as one standard atmosphere of pressure which is about 760 mm Hg absolute pressure. If you are capable of removing all gas particles from a space, then you will achieve -760 mm Hg gauge pressure, but you cannot ...

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Suppose you have a box filled with water in a uniform fashion. Now if you try to stretch the box in the $z$-direction, say, while keeping the other dimensions constant, what is the energy required? Well if the water distribution remains uniform, you can approximate this by the Hookean law $E_\text{elastic} = \frac{1}{2}k(z-z_0)^2$. Note that the constant $k$ ...

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I guess the force due to pressure on the hemispherical portion at the base is equal to the weight of the fluid. You can just calculate the volume of the fluid and multiply by $\rho g$.

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Test data shows that pressure on ground is calculated by dividing the weight of car divided by 4 then divided by patch area which will always be much less that the interior tire pressure. Test data shows that when the load is doubled the patch area only increases by 25%. e.g. under a 1000 pound load on tire the patch area is 100 sq.in while for a 2000 ...

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Yes, your idea would work, and it does save a bit of energy though not much. Suppose we are making water by reverse osmosis at sea level. We have to pressurise the water to around 6.2MPa (900 psi) so the work needed to produce 1 cubic metre of fresh water is 6.2MJ. Now let's do it your way. Let's assume already have a shaft sunk into the sea so we'll won't ...

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There is a model described in Main's Vibrations and Waves in Physics dealing with the speed of sound variations you might consider useful. Sorry, I would just comment that, but I don't have enough reputation. The other way might be to derive the speed of sound not from the ideal gas laws but from van der Waals equation, but to be honest, I've never tried ...

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The very famous Newton-Laplace equation is a relation between the speed of sound and the pressure of an ideal gas. It can be written as: $$v = \sqrt{\gamma P / \rho}$$ where v is the velocity of sound in the given medium, P is the pressure, γ is the ratio of the heat capacities for the medium and ρ is the density of the medium. The Newton-Laplace was ...

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Bad Things Happen The air, as it has no pressure or enough gravity to keep it in the ship, will attempt to expand. Air, in fact, attempts to expand to fill the container it is placed in. If there is no walls to the container, like on a planet, it will only be stopped by gravity. When the airlock is unsafely open or a hole is made in a spaceship, the air ...

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