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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28 views

Find the density of air at the given temperature and pressure

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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Air pressure in bars body [closed]

Good morning all, How do you calculate the air pressure exerted on an average human of 1.9m2 I know the air pressure is 1.01kPa. Do I do, F = PA? 1.01kPa x 1.9? What are the calculations step by ...
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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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34 views

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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1answer
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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 ...
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Is there an influence of the air humidity on the air expansion by a temperature change?

I have found the following formula to calculate the expansion of air by a temperature change, if the pressure stays at the same level: ΔV = ​ɣ * V0 * ΔT This would give me an expansion of 46.96m3 in ...
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If eardrum vibrates when hit, why don't we hear the air in the room that is continuously moving? [duplicate]

The eardrum is pretty thin.Therefore it should be very sensitive to movement.So, why don't we hear the air that is constantly moving.My guess is that the force of air pressure is not enough.Maybe I am ...
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Can cooling airflow be too fast for efficiency?

If using pressurized air flow to cool a hot metal tube (by blowing the air through the tube, not blowing it over the exterior), would high volume fast airflow cool better than low volume slower air ...
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How can a constant mass flow rate of air coming out of a compressed air tank be maintained? [closed]

If I have an air tank filled with air at, say, 4 bar, how would I be able to maintain a constant mass flow rate coming out of that tank, with the air flowing out into the atmosphere? I would imagine ...
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Why does sound behave differently in water than in air?

I noticed in some experiments at home that sound does not behave the same in water than in air. Is there a good scientific explanation to this? I noticed that the sound sounded distorted in water but ...
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What is the mass of a volume of air? [closed]

Google says 1 cubic meter of air has 1 kg of mass at room temp. This seems like garbage, as if the container is supplying the mass. But if there is no container, it cannot take 1 kg of pressure to ...
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Relationship between CO2 concentration and thermal conductivity of the air in a volume?

How much would the percentage of CO2 in a room need to change in order to make a measurable change (using transient hot wire method) to the thermal conductivity of the air inside room? Are there other ...
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Finding the drag force from the final velocity of a falling object

I know the velocities (v) of an object after it fell for respective distances (s). From that alone, is it possible to calculate the drag force at a specific moment in time? If not what else would I ...
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Water / Air flow via thermal difference

This is a simple water/air flow thought experiment I had that I'd like to understand better... The basic idea is that you have a closed loop of water or air standing vertically. One side is heated to ...
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Do CFCs get emitted in air from appliances?

Do the refrigerators and air conditioners that use CFC or HCFC cause damage to the environment even when they are working normally. I mean, is there any gas emission under normal conditions when the ...
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Why are we able to see air bubbles under water?

Title is self explanatory. I'm assuming both water and air are transparent. So, if they are true, how can I clearly distinguish an air bubble under water?
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When is it more efficient to blow air over a wet laundry in order to dry it - when it's wetter or when it's drier?

If I want to speed the drying of laundry and allocate for it one hour of fanning - should I use it just after I hang it to dry or several hours later? When we want to cool hot tea it's better to add ...
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How does flatulence travel through the room when opening a window? [duplicate]

When the smell in my room seems to be full of flatulence(it wasn't me), what happens with the gases when I open a window? Detail: It is winter and the air outside is cold whereas the air in the room ...
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Increase Air Speed at outlet

I have a set up that inflates a rubber jacket in order release the metallic rings from underneath it. I am currently having issues with not having enough pressure (force) at the outlet to inflate the ...
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Why do thermal currents affect light but wind does not?

I notice if I put heat under a laser beam it will cause the beam to shimmer. The heated air is causing a disturbance in the air which affects the light. Yet, I can blast a stream of air from a ...
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Simple experiment proving air pressure is stronger than water pressure at sea level [closed]

I conducted a simple experiment I: pour a little of water into a cup, put a card on top & turn all upside down. The card does not fall $\Rightarrow$ $$P_i + P_w < P_o\tag{1}$$ $P_i$ : air ...
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Tire pressure physics

I understand that with less tire pressure you get more surface area on the pavement and more friction which gives more rolling resistance, but does having less air mean that there’s more weight per ...