Questions tagged [air]
Earth's atmosphere is a layer of gases that surround it, permitting life and protecting life by absorbing ultraviolet solar radiation, warming the surface by retaining the heat and mitigating the temperature difference between day and night.
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What makes air exist as a physical yet almost homogeneous mixture with no difference in concentration across regions?
You would think air being a physical mixture there would be changes in N2:O2 molar ratio across regions. But we all breathe more or less same composition of air, right? How come?
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When the air can be regard as incompressible and how to get this conclusion?
The air density changes negligibly when the air velocity $<0.3$ Sound velocity, so in this case it can be regarded as incompressible, How to get to this conclusion?
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What kind of vacuum would you achieve if you used a compressor in reverse rated at 8 $\rm bar$? (centrifugal, piston or axial if it matters) [closed]
If you used for example a centrifugal compressor that compresses air from an intake of 1bar to 8bar in reverse, what would be the vacuum achieved in mbars? Can a compressor even work with an ...
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How do I extrapolate a value of oxygen particles per million from vacuum pressure Pa/torr
If I have a box of 40 $\text{cm}^3$, with ambient pressure and oxygen, how could I extrapolate and bring down the oxygen level to say 500 ppm from an equation such as $1.33 \times 10^{-4}$ Pa ($1 \...
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Within close proximity, how much does the atmosphere influence light and thus what we see?
Not sure if this is the best place to ask. Apologies if not.
(Assume this is under generally average conditions)
Say you have an object that is 1 metre in front of you. When you see that object, how ...
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The suction and thrust of an aircraft engine
Does only the air sucked in (not the air that is ejected at the back of the engine) by an airliner engine (turbofan engine) causes a thrust forward or in other words pull the engine forward? and why ?
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Is atmospheric pressure on an object in vertical plane equal to that of horizontal plane? [duplicate]
Suppose there is a cubic object placed at a surface level. Will the atmospheric pressure exerted on the upper surface of it be equal to that of the pressure exerted on its sides?
As far as I know ...
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Filling the empty bottle with hot air
If I were to fill the empty empty bottle with hot air, how can it be done? If I leave the bottle out in the sunny weather, will the bottle fill with hot air?
When I am filling the empty bottle with ...
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What makes longitudinal waves work?
I am quite confused by what makes a wavefront that is part of the compression (line A) turn back towards the rarefaction area. Lets say that the sound is propagating left to right in the image:
What ...
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Does it follow that hot air is always replaced by cold air? [closed]
A cylinder contains a powder made up two substances - spherical grains of metal and spherical grains of plastic. In between the grains are voids, so that the cylinder is made up of 75% powder grains ...
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Can you make $\rm H_2O$ out of the air with tools anyone has? [closed]
I was just wondering if you could make $\rm H_2O$ out of the air with tools that everyone has?
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Why do raindrops look like sticks?
I always thought that raindrops look like this emoji 💧.
But today, I shot it in slow-mo (see on YouTube), and they look more like sticks.
Was it some light effect of my camera, or do they really look ...
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UV-absorption capability of air
I am looking for an absorption chart for UV light with a wavelength of around 250 nm in air (ambient, no specific preparation). How much of a beam of this light would be absorbed per meter of path ...
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If you decreased the mass of a planet, but kept the mass of the atmosphere the same, would the air density decrease?
So, I know that atmospheric pressure is a result of both the atmospheric mass and the force of gravity acting on it. If you were to decrease a planet's gravity, but keep the atmospheric mass the same, ...
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Snorkeling vs diving with a breathing cylinder
If diving with 5m snorkeling pipe our lungs would collapse due to 0.5 atm difference, right?
If diving with a cylinder that has air with atmospheric pressure (the pressure our lungs can use), we can ...
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Is it possible make a train moving with less atmospheric friction if a pressurized air shield is applied at its frontal part?
Like the magnetic field blocks radiation particles approaching Earth could a pressurized air pipe at the frontal part of a train block atmosphere that constantly slows down that train? The pipe should ...
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Dust Estimation technique
I'm comparing different coating agents for ammonium sulfate fertilizer granules, coating agent is an additive to limit the dust emission, so I have a new coating agent that is lower cost and more ...
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Why do clouds have well-defined boundaries?
Why do cumulus clouds have well defined boundaries? In other words, what are the physical mechanisms that hold a cloud together, as an entity separate from other clouds, that prevent it from spreading,...
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Equation for Velocity of air and Pressure difference
Whenever there is a pressure difference, air will flow from the high pressure (area/point) to low pressure (area/point).
I am looking for the equation that relates the velocity of air to the pressure ...
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Could a glass cup containing a vacuum rise into the air?
https://what-if.xkcd.com/6/ has been mentioned here before, but I'm questioning whether or not the glass cup with the bottom half as a vacuum would rise at all.
To start with, a vacuum exerts no force....
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Optimisation of pop pop boat?
This beautiful video of Steve Mould explains the working of a pop pop boat using a glass boat.
Now he explains that the pop pop boat doesn't move because of ejecting water in one direction like a ...
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How, if, does the inside air of a football influence it's motion?
And before me lies a football. Say it's filled with pressurized air. If I kick it, how will the inside air be influenced? Will the kick induce soundwaves? Can the ball give a sound? Will it influence ...
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Why doesn't an air valve move automatically when placed on a zero friction surface?
Air pressure is actually a force experienced by the surface of the container when air molecules hit it in high speeds.
An air valve opens and allows air to move in one direction and blocks the the ...
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How to harvest water passivley?
I have been reading recently about methods to collect moisture from the air passively and turn it into water. However, is there any attempt currently for small-scale water harvesting?
Methods I have ...
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What is the theoretical range of temperature the air must be in order to reflect/refract light (for a volumetric display)?
Well, the only question I found in this website about volumetric displays on air was this one, but it specifically suggests making air denser in order to make it work, but my question is specifically ...
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Why does Hoberman sphere open when thrown up? [closed]
Please try and explain this to a dummy :) I haven’t had any university level physics education, at least yet.
I was messing around with a mega sphere (Hoberman sphere toy) at a family dinner when I ...
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Equilibrium of air volume in and out of an inflated bag
I want to use a small squirrel cage fan to blow air into (and inflate) a closed bag. The bag will also have a number of small holes in it to release air at various points across the bag. But, I want ...
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How to Model the Forces within Inflatable Tube Man
I have a CPP setup for a cloth simulation. Currently it takes in forces for wind simulation and gravity and these forces act on individual "point masses". I'm trying to figure out how to ...
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Hole in Bernoulli's theorem when trying to blow ball into bottle
According to Bernoulli's theorem while blowing a paper ball inside the bottle (as shown in this short video), the speed of the air at the mouth of bottle is higher and hence creates low pressure ...
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How does air cool as it nears the poles?
I understand air is heated by the equator causing it to rise towards the poles. But why does air cool and sink after nearing the poles. Shouldn't the air still possess heat, after being heated by the ...
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Warm air syphon to cool down greenhouse
I'm thinking about a very energy efficient way of controlling temperature inside a greenhouse when it's too hot.
The goal is to use the syphon effect in order to draw hot air from the top of the ...
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How does (air) pressure balance under constraints?
I'm playing around with building a very basic simulation of (air) pressure in a grid environment.
The idea is that I have this 2d (or 3d) grid of cells. Each cell has a certain atmosphere.
Between the ...
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Do forests create wind?
Forests evapotranspire more water vapor into air than surrounding areas, have more clouds, and are usually cooler (because of evaporative cooling). How does this affect the air pressure of forests? ...
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Why doesn't pressure affect the speed of sound in air? [duplicate]
I keep getting the answer "because density increases when pressure increases" but that doesn't really make sense to me since in denser materials - like water - sound travels faster. And if ...
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How come air masses displace air when it moves rather than mixing with it? [duplicate]
It seems if you had one mass or air moving towards another air mass, that the molecules within that first air mass would be able to penetrate into the second air mass because the distance between air ...
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Can Stoke's Law of Viscous Force be applied to freely faaling body?
As air is a viscous fluid can we apply Stokes Law to freely falling bodies. By doing this we can see that the velocity of a freely falling body doesn't increase with time but it stops increasing after ...
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Why not a heat pump with only the outdoor air?
I was wondering why we can not use only the outside air for a heat pump? Taking the outside air, pass it through a compressor to increase pressure and temperature. Then the hot air flow heats the area,...
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Bird drink feeder -- How to make water come out automatically and stop coming out from a bottle? [duplicate]
I am watching a video about a DIY bird water feeder.
https://www.youtube.com/watch?v=q6EitavSRNg
In the video, three holes were punched from the plastic bottle in a triangular pattern, and then the ...
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Why is ozone $\rm O_3$ in the Earth's upper atmosphere?
If you look at the density table, you will see that ozone has the highest density among other gases, so why is it in the upper layer of the atmosphere, in the picture I schematically drew how the ...
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Room ventilation during summer
I can never get this right =)
I have a main living room with air con running in summer. But CO2 levels build up.
Now its evening and I want to vent the room but without the room getting too hot again (...
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Can you remove air bubbles from oil by heating it just like you do with water? Does oil even have dissolved air?
I have a flat bottle filled half with water and top half with oil. It has a impeller connected with motor which slowly swirls oil and water to create beautiful lava lamp like effect. However after ...
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Thermal power station powered by temperature difference between high and low altitude air
Would it be feasible to build a system where warm air from sea level is pumped to the top of a mountain to power a thermal power station?
With a lapse rate of ~ 1°C / 100 m there should be plenty of ...
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Equation to find the velocity of gas
Air travels from a hot place to a cold place.
Is there an equation that shows the relation between velocity of gas (specifically air) and difference of temperature between two points?
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Does indoor odor smell travel up or down?
Does odor smell, let's say it's from caulk off-gasing, travel upward or downward in the air?
Are all odor smell lighter than air?
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Would lotion pumps work in a vacuum?
I'm just trying to understand how a lotion pump works. I watched this video and it's explained that it's due to the difference in air pressure.
https://www.youtube.com/watch?v=EJVL5zXIPLA&...
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Ventilation - Push system into Pull system, what can happen [closed]
this is my first question so please go easy on me.
I have a system where it pulls air out of a sealed box at ~500l/min (this sealed box has a requested pressure of 10Pa, in case it is relevant).
The ...
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At what speed would a wind affect a bullet? [closed]
Firing a gun loaded with the fastest bullet (.220 Swift 1,422m/s or any bullet that is super fast and excellent aero dynamics) in a close range (2cm) from the tip of an air blower. What would be the ...
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Does the amount of oxygen in air, actually get lower as you go to higher altitudes?
I have heard that there is less oxygen as you go higher (that's what my teacher told me). A reason that supports that is, as you go to higher altitudes, it becomes more and more difficult to breathe. ...
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How does a virus fall down in static air?
If we drop a virus from a height, in static air, will it fall to the ground like a lead ball, a balloon, or like a virus? How will it fall to the bottom? Like a Brownian particle? It will not float ...
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Could super-heated gas allow for Dirigibles/Zeppelins/Balloons to go higher than 60 km of altitude?
Well, I don't know much about physics in general, so I hope I don't make too many misconceptions.
So, from what I could read in this Wikipedia article, the balloon named "BU60-1" achieved ...