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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10 views

Air resistance of a high velocity cone

This is research for a speculative fiction device. A cone (whose height and radius is on the order of metres, mass in tens of kilograms) flies point-first through air (equal or somewhat less than ...
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How much would increased gravity affect the particle count in air?

If everything else on Earth stayed the same (as much as possible anyway) but the mass was scaled up, how much would that affect the number of non-gas particles in the air such as dust, hairs, viruses, ...
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Why does moving air feel colder? [duplicate]

If temperature is just the average kinetic energy of particles, why would moving air feel colder rather than warmer?
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Why do all heavier gases in the atmosphere not settle down to the surface? [duplicate]

Some pollutants heavier than air that are released into the atmosphere include $\text{CO}_2,\text{SO}_2,\text{SO}_3,\text{NO}_2$ etc. Since these gases are heavier than air, Why do they not settle ...
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2 gallon tank pressurized to 100 psi connected with a tube to a tractor tire with only 30 psi

2 gallon tank pressurized to 100 psi connected with a tube to a large tractor tire with only 30 psi. And the air does not move from tank to tire. Why? Can anyone link a YouTube video to explain ...
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How to calculate air density at altitudes higher than 86km?

Barometric formula is fit up to 86km. Is there a sufficiently nice approximation for what happens above (e.g. thermosphere where molar mass isn't constant anymore)? I understand air is much thinner ...
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Question about a theoretical bee's power to lift

Given a theoretical bee with sufficient (not limited) wing power and material strength of the wing, but with realistic dimensions is it possible for it to lift a human? If not, what are the ...
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When should I open/close the windows/curtains to keep the room cool in summer?

Folk wisdom has it that in order to keep your room cool, it's best to close the window. I assume the reasoning is that while a breeze of air feels cool, in most traditional houses the outside air ...
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Pneumatic flow formula

I'm looking for a pneumatic formula in order to have the flow. I found many formula, but only for hydraulic : $\Delta P = R_p Q$ where $R_p$ is the resistance, $Q$ the flow, and $\Delta P$ the ...
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What's the speed of change of the relative humidity of air inside a greenhouse [closed]

The propagation speed of air humidity is an important variable affecting climate and sanity inside a greenhouse. High relative humidity of internal air is a typical phenomenon of many greenhouses ...
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For a given volume of air and water, which would heat up faster?

Based on a discussion I had with a friend over dinner tonight - he thinks water will because of the high conductivity, and i think air will, because even though it has lower heat capacity, the same ...
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Why does this ducted fan have 10 blades (instead of some odd number of blades)? [closed]

I've searched online and learnt that odd number of blades reduce turbulence and noise. I counted my home's ceiling fan, it has 3 blades, then I counted my laptop's fan, 13 blades! Amazing! But later, ...
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SARS-CoV-2 virus floating in the air in *aerosols* for up to 3 hours [closed]

Good evening/morning. I have a question related to SARS-CoV-2 virus spreaded in the air. This Straits Time article from March 18 describes a new study: The tests show that when the virus is ...
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What is the effect of dust particles on air pressure?

Is there any change of atmospheric air pressure if dust particles are present (which really does)?
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Why is the direction of cathode rays independent of the position of anode?

The following statement is from the book Concepts of Physics Volume 2, by Dr. H.C. Verma, chapter 41 - "Electric Current through Gases", topic "Cathode Rays", page 343: Cathode rays are emitted ...
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Why does the breakdown voltage increase when the separation between the electrodes is decreased beyond a particular value?

When I was learning about Paschen's law from Wikipedia, I came across the following statement: Paschen studied the breakdown voltage of various gases between parallel metal plates as the gas ...
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Could there theoretically exist a material so light, that it can levitate in the air just due to the in height decreasing air pressure? [closed]

Airplanes can fly because the pressure on the top of the wing is lower than on the bottom. But the difference in pressure must be huge in order to lift an enire airplane. Also, the difference in air ...
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Why particles stay suspended in the air and seems separated from the other layers of the atmosphere?

Example: in the following image: you can see that particles are suspended at a certain height, but they don't keep floating beyond - like, a ballon (best comparassion I can make). I wonder what are ...
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Is static electricity an “electrical discharge”?

I understand that any electrical discharge such as corona discharge is the scattering of electrical charge through a medium; most likely a gas ("discharging charges"). As the air is a gas, would it ...
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1answer
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Balloon with attached strip in the wind

I was asked a bit trivial question, but am failing to decide what is the right answer. Suppose I have a balloon [inflated with a lighter than air gas] and a strip, maybe a very light flag attached, ...
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What happens to oxygen during atmospheric absorption of radiation with a peak at 60 GHz

This question discusses atmospheric absorption of radiation (specifically 5G radio waves) due to oxygen at 60 GHz. I would like to know exactly what happens to oxygen in all its forms (be it air or ...
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1answer
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Air bubble trapped inside water at the spout of water tap

Is there a name for this effect and how is it formed?
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1answer
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Air pressure dependence on temperature

I have around 200 barometers (altitude up to 200 m above sea-level) of which some in direct sunlight that can become relatively hot. I am investigating whether there is any relation between measured ...
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Moisture diffusion in air

Moist air is less dense than dry air. Additionally hot air is less dense than cold air. If we have moist hot air packets above dry cold air packets. How can the mixture of these air layers be ...
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Cooling down room with just a water

As I know, heat capacity of normal air is ~1kJ/kg and heat capacity of water is ~4.1kJ/kg. I am trying to cool down room (around 6m³) from 30C to 20C just by cold water. Let's say I have water with ...
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Why doesn't the atmosphere separate according to density? [duplicate]

Why don't dense gas elements sink to the ground and dense gas elements drift to the sky? Why don't we have layers of oxygen, nitrogen, carbon dioxide, etc.
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What is the formula of ratio of pressure between nodes and antinodes of a standing air wave?

On the internet I haven't found any formula related to pressure ratio of nodes and antinodes in a standing air wave. And what is is the dependency of that ratio on the frequency of standing wave. ...
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What is the air pressure on a magic wall that reflects all incident molecules perpendicularly to itself?

I am a total laywoman in physics and humbly hope that physics experts of this SE can help me find the answer tо my question. A friend of mine and I had an argument about that question, and I am very ...
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Reason for lower air pressure above an airplane wing

I am posing this question from the perspective of a novice. I read an article, from Scientific American, titled "No One Can Explain Why Planes Stay in the Air". The article explains how, while we ...
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Reducing jet mixing

I am trying to develop an annular nozzle for Nitrogen gas. My target is that Nitrogen should not mix as much possible with surrounding air. I understand that shear layer increases mixing. Is there a ...
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How to calculate CFM of cooling fan using anemometer and duct?

I have quite a few 4010 (40x40x10mm) fans and would like to measure the air flow of each one. I have designed this 3D Printed duct that fits on a handheld anemometer, and the fan mounts on the other ...
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Influence of ultrasound on air pressure levels

I am wondering if Ultrasonic waves can influence air pressure. Would there be change in air pressure in the order of Pascals where ultrasound waves pass?
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Is ionized air ferromagnetic?

We know that ionized air is a good electrical conductor, but is it ferromagnetic? Can it be magnetized?
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Does an A/C change the pressure of a sealed room?

Since I don't know anything about air conditioners, I thought you might have an answer. I noticed that when my A/C is on and all the windows and doors are closed it is actually working for a few ...
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Can a balloon filled with air float because of the moisture content of air in and around it?

I assume dry and moist air are different in density. Is that difference large enough to make a balloon float? I mean moist air in terms of relative humidity, as is used when talking about weather. ...
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Mean free path for charged molecule inside air

Question I would like to compute the mean free path ($\lambda$) for a "heavy" charged molecule ($M$amu, $q$ charge) in a low pressure gaz (air, but also ions such as Ca$^+$). I think I figured out ...
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Gas Flow Rate and Pressure Difference

I have a pipe with two ends and on each end the pressure of the air is different. Is there any relation that can tell me the flow rate/speed of air inside the pipe because of the difference in ...
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Misconception about air pressure

I have heard that our ear pops at high altitude cause of change in air pressure, air pressure outside your eardrums needs to equalize with air pressure inside your eardrums, however, gravity pulls the ...
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Why does the cold air coming down from an ice cream oscillate?

It occurred to me that when I held a choc-ice the other day (a wooden paddle with a chocolate ice-cream above it with two large smooth sides) that I could occasionally feel cold air falling down onto ...
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Air resistance in multirotor aerial vehicle (MAV)

Im modeling the aerodynamic friction (translational and rotational) that affects a quadrotor in movement. I think that I can approximate it with a constant multiplied by linear or rotation velocity ...
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What would happen if you drop two objects of the same shape and size but different mass in Earth's atmosphere?

The question of letting two objects fall in vacuum and the effects on gravity is discussed on this site including questions like the gravitational pull of the objects towards each other, the Earth's ...
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Is it possible to produce shock waves in air using low intensity pulsed lasers?

Air has about 0.04% carbon dioxide. Carbon dioxide has a very strong absorption band around 4.2µm. Let's say I used a nanosecond pulsed 4.2µm MIR source and targeted it into air, part of this would be ...
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Is it possible for temperature to cause a change in the density of air in a closed isochoric system?

I am taking a meteorology chair as part of a airline transport pilot course and while discussing atmospheric pressure and density the professor claimed that an increase in the temperature of the air ...
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Why do far sound getting sometime louder and sometime fainter?

Actually I was walking on my roof and have heard some kind song coming from far distant loud speaker. Which getting louder sometime(sometime air blowing to me at that instant) and sometime getting ...
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Air penetration of filter in pipe with fan

Air is forced down a pipe by a powerful fan. A filter with considerable wind resistance can be alternately mounted inside the pipe at either end. Will the same amount of air throughput occur with the ...
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Why does the speed of sound decrease at high altitudes although the air density decreases?

I understand that the speed of sound is inversely proportional to the density of the medium as shown here and as answered for this question. The problem now is that the speed of sound in air actually ...
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Continuously cooling air at the entry to a vertical tube to get a denser air flow at exit

If you have a well insulated vertically aligned pipe open at the top and bottom to ambient air, and then continuously cool the air at the top entry cross-sectional diameter to create a free-falling ...
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Heat reduction based on compression

So I was thinking about air conditioner today and how we run air across compressed freon to cool down air but why do we need freon at all why not store just compressed air. My guess is because its ...
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Why does the “air” close or open doors?

Assume we have an empty room with two doors on the opposite sides of it. If we open one of the doors, the door on the opposite side automatically closes "harder", and if we close one of the doors the ...
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Will a sealed container resist the change in air pressure on a plane for liquid/air mixed bottles?

I want a way when traveling to not have to worry about the change in air pressure for my liquids. I vape using pods, and have a few different ones for different flavors. The problem is when I go on ...

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