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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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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105 votes
4 answers
10k views

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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2 votes
3 answers
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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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1 answer
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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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1 vote
1 answer
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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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1 answer
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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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2 votes
1 answer
37 views

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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Depressurization formula for multiple holes with varying outside pressures

I'm working on a simulation that should with relative accuracy simulate the flow of air/pressure in a system of rooms (on a space ship). I found http://www.spaceacademy.net.au/flight/emg/spcdp.htm ...
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1 vote
1 answer
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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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1 vote
1 answer
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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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Why does sound travel faster in helium than in air? [duplicate]

Sound wave travel faster in solid than in liquid, and travel in air with the slowest speed because solid is denser than liquid and liquid is denser than air. So, sound wave speed should be faster in ...
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1 answer
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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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1 answer
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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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2 votes
2 answers
103 views

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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1 answer
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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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1 answer
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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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2 answers
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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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4 votes
1 answer
92 views

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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2 answers
36 views

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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3 answers
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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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0 answers
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Calculation of dry air density without relative humidity

I would like to estimate the density of dry air at different temperatures and constant pressure (1 bar) just using the densities of nitrogen (79%) and oxygen (21%). I consider the number of other ...
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1 vote
2 answers
67 views

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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3 votes
2 answers
104 views

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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20 votes
4 answers
5k views

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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16 votes
3 answers
2k views

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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2 votes
2 answers
51 views

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 ...
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2 votes
2 answers
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Flattening a sealed bag in space

Let's say you're in space, and you have an empty, sealed, round bag in space (full of "nothing" since there's no air). Is it possible to flatten the bag without unsealing it? My ...
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0 votes
1 answer
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What actually happening in land breeze?

From childhood we are taught about land breeze and sea breeze , but I always had a doubt. Look at diagram Book just say " air above ocean become warm so it rise up creating a low pressure zone ...
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0 answers
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What is the relationship between air temperature and updraft velocity?

So I was playing Zelda Breath Of The Wild recently. And in the game, you can set grass on fire to create an updraft. (see the gif below) Which led me to ask myself : "Wait, how hot are these ...
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8 votes
1 answer
362 views

Is rising air high pressure or low pressure?

I keep hearing people saying that air rises because it is low pressure and that's what causes clouds to be formed. But, isn't hot, rising air high pressure? It's got fast moving atoms in it and that ...
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26 votes
3 answers
5k views

What is cold wind?

As per my understanding, temperature is the movement of particles in an environment. A highly energetic environment where particles possess high energy has a high temperature, and low energy means low ...
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2 votes
2 answers
98 views

Why is air considered to rise adiabatically?

Do air parcels not push against other air and do work on them? When air molecules within an air parcel bump into air molecules outside the air parcel do they not transfer energy to them?
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1 vote
4 answers
2k views

Why doesn't a hot air balloon burst even if we keep heating the air in balloon for a long time , shouldn't the air pressure become so high to resist?

I don't get one thing: we say a hot air balloon rises as hot air is less dense than cooler air. However, if the heat source continues to add heat to the air in the balloon, doesn't the hot air become ...
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-6 votes
2 answers
83 views

Are air particles massless? [closed]

so as the question suggests, I wanna know whether an air particle has mass or no. Thank you!
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0 answers
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How to find at what rate of air flow the pressure in the system is maintained?

I have a pump that is pumping air into a vessel that has an inlet and an outlet. I have the experimental values for the point where the flow rate maintains the pressure but I can't figure out how to ...
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1 vote
4 answers
313 views

Why is the force due to a vacuum in a syringe so much greater than the force due to the air being compressed in the syringe?

I'm a teacher using a plastic syringe (no needle) to demonstrate the compressibility of air and the incompressibility of water. Works great, they can push the plunger in while blocking the end of the ...
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0 votes
0 answers
47 views

Will Air pockets replenish oxygen?

Assume I am stuck in an underwater cave that has an air pocket. I stayed there for a couple of days and got rescued just with very little oxygen. Will the oxygen replenish in the cave? Do we have any ...
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5 votes
3 answers
690 views

When and how was it 'concluded' that there is no air in space?

When was it confirmed/concluded that there is definitely not air in space? And how was the conclusion reached? We see the discussion of 'ether' before Special Theory Of Relativity and there it seems ...
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2 votes
1 answer
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Can a dehumidifier reducing household energy consumption? Debunk this claim [closed]

I have recently bought a dehumidifier to control humidity in the winter, prevent mould and stop windows steaming up. Claims of reduced heating cost I noticed when looking what to buy, that some claim ...
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0 votes
2 answers
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Heating air inside a drum to raise pressure [closed]

Hi and thanks for adding me. I have a complicated question! I hope it's not too complicated for someone out there to help me! So here's the situation. I work in pharma and we supply drums to customers ...
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