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2

First and foremost, a primer over what "buoyancy" is is needed. Pressure decreases with altitude. The atmospheric pressure at the top of the balloon is a tiny bit less than the atmospheric pressure at the bottom of the balloon. This pressure difference results in a tiny net upward force on the balloon. The balloon rises if this tiny net upward force exceeds ...


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To see if this is possible we can use a formal material selection approach of the kind presented in "Material Selection in Mechanical Design", Elsevier, M.F.Ashby. Our objective is to maximize buoyancy while keeping within the no-buckling constraint. To make things easier I suggest some simplifications. First, Poisson's Ratio does not vary much for most ...


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The relative humidity of air is pressure dependent. Your method of popping your ears involves increasing the pressure of the air in your mouth. And if you sufficiently compress a volume of air that has a high relative humidity, you can increase the air's relative humidity beyond it's saturation limit, which causes the water vapor in the air to start to ...


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I know that air pressure and temperature are inversely proportional. You should not know that. This is the source of your misunderstanding. The ideal gas law, $PV=nRT$, can be rewritten as $P=\frac R m \rho T$, where $m$ is the average mass of a molecule in the gas and $\rho$ is the density of the gas. The first term on the right is a constant for a ...


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As mentioned in the other answer, additional air is being entrained. This principle can be used to produce considerable flows and considerable pressure differences. Examples In a steam locomotive, the exhaust steam from the cylinders is directed to a nozzle that points upwards towards the exit of the funnel. This draws the smoke through the boiler and ...


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Very interesting observation. I think what you are observing when your mouth is away from the tube is MORE than just the air you exhale - because the air in the vicinity of your breath is being "dragged along" by something called "entrainment". This is the principle behind an ingenious fan, called the Dyson Air Multiplier: A detailed explanation of how it ...


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What a layman calls "air resistance", a physicist would call drag. Drag is affected by the area and shape of the solid object, the speed and orientation of the object relative to the fluid, and various properties of the fluid such as its density and kinematic viscosity. The drag on a solid, rigid object isn't affected by the object's mass. However, drag ...


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A breeze at 35°C and 90% humidity (typical conditions in Houston, Texas) doesn't cool you off. It just makes you feel even more miserable. A breeze at 40°C and 20% humidity (typical conditions in Phoenix, Arizona) doesn't cool you off, either. It, too, just makes you feel even more miserable. Your body cooled because the air velocity was much lower than the ...


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There are several major difference between the asteroid and you. You have moisture on the skin. As the air passes over the skin, it picks up the moisture, making you feel cooler. The asteroids are travelling hundreds of times faster. The compression of air increases the heat substantially. You would barely notice the heat increase from a car.


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I've found in this website an interesting plot. In particular figure 12 shows some polar curves vs weight*: It is possible to note that bigger weights requires more engine power to maintain the altitude for every given fixed speed. Plus we must take into account the extra fuel spent to take an extra bag from ground to 900 km/h at 12 km altitude (that ...


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Some numerical values: Althought he didn't explain his calculations, according to Tony Webber, former Qantas Group chief economist the costs of 2 extra kilograms are: These increases represent weight gains of around 0.23 per cent and 0.20 per year for woman and men, respectively. Since 2000, the extra loading that an average adult passenger carries is ...



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