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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105 views

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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Dependence of Coanda effect on radius

I'm doing experiments to find out when a candle blows out when a round obstacle, like a bottle, is placed in front of it. Is there any mathematical model to determine how the radius of the obstacle ...
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Why moving train's windows slam shut when another train passes slowly in the same direction?

My question is related to this one but distinct as this case is trains travelling in the same direction. We're familiar with this scenario. You're sitting in train A and another passes at high speed ...
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Air-Water mix flow and pressure

I'm using a system that creates water and air jets. The air line pressure is constant at 1.5 bar while the flow rate changes between 100-2500 cm³. The mixing is done with a water pump that operates ...
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Can you see the wind?

So one day when I was at the beach, I looked toward a parking lot and could see the wind. It wasn't heatwaves, as it wasn't hot. I'm doing something about this for a summer homework project, and I ...
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Is this cheap “air conditioner” able to cool a room?

My parents bought this "air conditioner", but I am very skeptical that this can cool a room, or even cool anything. I doubt that it even has a cooling element, I suspect that it is just a fan + ...
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Does Betz's law apply when the turbine is moving

So the Betz's law indicates that the maximum air turbine efficiency is 59.3%. Imagine if the turbine is moving towards air, not the other way around, does this law still apply in this case? Thank ...
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Heating outside air - how much humidity can it take?

I am trying to figure out this problem - maybe it is simple for someone of you but I can't figure it out. I have known variables of outside air temperature and relative humidity (RH), I am taking ...
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Does warmer air of the same humidity condense faster?

Warmer air can hold more moisture but can it also release it's moisture faster when touching a cold surface? If air is warmed (for example by the hot side of a thermoelectric cooler ) before it moves ...
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Find the density of air at the given temperature and pressure [closed]

Find the density of air at $99$ kPa and $322.15$ K. My attempt: Let's assume that air is $78\%$ nitrogen and $22\%$ oxygen by volume. Average molar mass of air = $0.78\times 28+0.22\times 32\approx ...
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calculate CFM of a ceiling fan

I'm trying to calculate, or even understand what data do i need to calculate the CFM of a ceiling fan. in many countries this is a given data in the product details but not where I'm from. I have the ...
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Acoustics air flow vs the human body

My question to you all is... Is it possible to move air acoustically. ie to move air over a 2.1m distance to be felt by the human body with a cooling effect but not heard by the human ear ? I'm just ...
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Why is it easier to catch mosquitoes with your hand when your hand is wet?

Recently I've noticed that it's significantly easier for me to catch a mosquito with my hand if my hand is very wet (e.g. from having washed my hands and not yet dried them, or from being in the ...
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How thick would the atmosphere have to be to block all the sunlight?

this is a question I haven't been able to find an answer to anywhere. How thick would our atmosphere have to be for the surface of the planet to be completely dark? Is that even possible? Thank you!
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Hypothetical question about a window for hot and loud places

So I live in a city that is rather warm at this time of year and the street where I live is rather loud. I have to keep the window in my bedroom open at night, otherwise it becomes way too hot. The ...
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Why does a helium balloon rise? [duplicate]

This may be silly question, but why does a helium ballon rise? I know it rises because helium is less dense than air. But what about the material of the ballon. It is made up of rubber/latex which is ...
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How do you calculate the speed of air when it fills a vacuum of 1 cm³?

At different heights, atmospheric pressure is different. If a vacuum was created of say 1 cm³, how would i calculate the velocity of air filling it back in. The adjacent layer of air would obviously ...
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Can air pressure be applied equality to a rail to lift a carriage?

There is a transport design that has a carriage suspended from a rail (A) that is levitated by pumping air through holes (B) into an area with the intention of levitating the carriage so that it can ...
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Tone production in Irish Flutes?

Since it's about a technical issue, I thought that this question would fit in here the best (as opposed to the music.stackexchange-site): I'd like to know how tone-production in an irish (wooden) ...
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How does the Torricelli barometer create a vacuum at the top of the tube? [closed]

Hi everyone! Can someone explain to me how does the Torricelli barometer creates a vacuum at the top of the tube? And how does it work?
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(Why) does wet air contain more oxygen?

I've heard the fact wet air contains more oxygen is the reason experts recommend to humidify the air. Intuitively, I'd say wet air should contain water of a greater density and thus, make less space ...
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Blowing smoke out of the clean air - can someone explain?

Yesterday my wife and I were out walking. The weather was cloudy and humid (it had been raining a few hours before). Around 15 C. Suddenly, with no apparent reason, both of us had smoke coming out ...
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Does the ideal gas law apply to a moving vehicle?

If for example you have a car travelling along a road. There is obviously a high pressure region in front of the car, where the air is forced around the vehicle. Likewise, I understand that cars will ...
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Low Air Pressure

Can we create low air pressure artificially in a system to make the wind blow towards the system from the higher normal air pressure in vicinity ?
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Air Flow through non-uniform size Duct with Holes

We are a manufacturing plant and this is one query which we could not find the answer too. So, came here asking for help. Problem: In the attached image, you can see the air/steam inlet from the top ...
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Individual air molecule momentum exchange

Background: Looking at this illustration about solar radiation pressure on a perfect reflective surface, incident photon exchanges its momentum to the slanted surface which provides a reaction force ...
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How do you find the minimum height to open a parachute for a safe landing?

What concepts/formulas can be used to find the optimum/minimum release height of a parachute?
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What is Work Done against the Atmosphere [closed]

{Assume it's a Spherical Balloon} The answer on the book states (7pV), but I'm definitely missing something. I've looked up online on what 'Workdone against atmosphere' means but there is little to ...
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How fast will air travel to fill a vacuum?

Suppose I have a sealed glass cylindrical vessel of radius r and length l that is evacuated. I smash one end. How long will it take for air to (a) reach the end of the cylinder (b) fill the vacuum ...
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Thrust needed from an engine to reach orbit

Assume you had an airplane with magical engines that didn't need fuel, air or power, to operate. What thrust to ground weight ratio would the airplane need to reach orbit? By ground weight I mean mass ...
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How to calculate mass proportions of each compound in air?

We know average volume proportions between compounds in dry air. Here are the more important (in terms of proportions) ones: How can we calculate mass proportions between these gases? I'm ...
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Calculating the power of a pneumatic piston vibrator

I am using a pneumatically-driven piston vibrator to compact a tank filled with granular material. The intensity of the vibrator can be regulated by changing the pressure of the pressurized air fed ...
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Insert sensors in an aerostat with helium?

Hy is possible for you insert sensors (to calculate pressure and temperature) inside an aerostat with helium ? I ask this because... I have an helium balloon anchored to the ground by a rope with a ...
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Does the supersonic aircraft feels less air resistance than when it flies with velocity less than sound

When ever I see pictures like this of some object flying at speed greater than sound , I see triangular waves . So I got question in my mind that Do supersonic objects weather its bullet or aircraft ...
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Is there any weight diffenence between sealed/unsealed bottles? [closed]

I have to prepare my chemical report about CO2 molecular mass. I searched and got a sample report from internet. I read it and I can't understand this. Weight of flask covered with glass cover = ...
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Thermodynamics - best fan speed to heat a room (for the same heating power)

Let's assume we have a cold empty room (with no person in it, therefore - barely little air movement) and we want to heat it up. In the room, we have a hot-air blower that has two fan speed-settings, ...
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Why is air pressure higher in winter than in summer?

At the top of a mountain, say Mt Everest, atmospheric pressure is low. So shouldn't the same thing be true for winter season. I.e air pressure in winters should be lesser than that in summers. But ...
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How loud does a sound need to be to make pressure waves detectable by a camera?

I've seen Veritasium's video that describes how sound can be picked up by a camera by observing small movements of objects sensitive to pressure changes (bag of chips, aluminium foil, paper...). That ...
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What causes my “kitchen witch” to move? [closed]

Not a physics person but curious about something going on and hoping someone can explain. I have a kitchen witch hanging from my kitchen ceiling on some fishing line and it’s constantly swaying and ...
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Air pressure drop off rate

I’ve been thinking about this for a while, and at first, I assumed that the inverse square law applied, but seeing as how air isn’t a form of radiation, I’m not sure that it still applies. So if we ...
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Why is blowing so different than sucking? [duplicate]

Why is it so easy to blow out a candle from a significant distance, but nearly impossible to suck enough air to do the same? Even without focusing the airflow through a nozzle or something, this ...