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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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How does the Torricelli barometer create a vacuum at the top of the tube?

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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Volumetric Flow with Air Compressor [on hold]

If I have a 5 gallon, 125 psi air compressor and I connect that to a pvc pipe with holes in it, how would I go about determining the amount of air flow through each hole in that pipe. It might be ...
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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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How many air molecules a second hit an adult's (average size) body's external surface? [closed]

given that they're in room conditions: room temperature (defined range is 20 to 25 °C): 20 dry air At 20 °C and 101.325 kPa, dry air has a density of 1.2041 kg/m³. speed of sound in dry air at 20 °...
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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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2answers
31 views

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 ...
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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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4answers
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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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1answer
31 views

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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74 views

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 ...
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1answer
51 views

Can we see stars in day time by making use of a blue notch-filter?

Given on a clear sunny day, the only light that is blocking the star light is the scattered blue light of atmosphere. If we make use of a notch filter, which blocks only the blue light, can we get ...
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1answer
127 views

Initial acceleration concerning free fall

I'm in the process of conducting research concerning free fall with air resistence. I'm dropping a beach ball filled with air from certain heigts, while measuring its speed and acceleration during the ...
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1answer
22 views

How is steam affected by a fan?

Scenario Consider a humidifier with a fan behind it. Assume same room, moderate temperature, low fan speed. ...
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1answer
93 views

Hydrostatic pressure in a gas

I have a physical picture of hydrostatic pressure ($dp/dh = \rho g$) in liquids, interpreting it as the weight of the water column. Now in a gas, the molecules are much further apart than in a liquid....
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1answer
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How to understand air pressure against a hand pump?

Imagine this little though experiment with me for a moment. A piston sort-of contraption - like a bicycle pump, but without any nozzle to push air out of. One foot tall, one inch width/depth. Lets ...
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For a lay person, what if there was no atmosphere? [closed]

What if there was no atmosphere (or little like on the moon)? Could I then hover above and watch the Earth below turn? Originally I queried, "why couldn't a person just float up in a balloon, hover ...
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2answers
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Air velocity flowing out of a pierced can [duplicate]

How can I calculate the velocity of air that would come out of a pierced can of compressed air if I assume that the pressure inside the can is 7 atm and the size of the hole is that of a regular nail?
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Simulating scintillation (twinkling)

i would like to set up a small lab experiment to try to create visible "terrestrial scintillation", whereby one can see fluctuations in air density (turbulent air), like the rear of the jet in this ...
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1answer
430 views

Why can't hot air balloons fly higher then helium balloons?

I have read these questions: Hot air balloon trajectory predictions Do atmospheric physics prevent hot air balloons from ascending over 60,000ft? What is precisely the reason that a helium balloon ...