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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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1answer
22 views

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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2answers
84 views

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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0answers
39 views

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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3answers
203 views

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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0answers
34 views

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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5answers
1k views

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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2answers
49 views

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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1answer
99 views

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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3answers
502 views

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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1answer
130 views

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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1answer
20 views

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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1answer
59 views

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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1answer
45 views

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
60 views

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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4answers
2k views

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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4answers
99 views

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
32 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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1answer
21 views

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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2answers
40 views

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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1answer
97 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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2answers
172 views

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
89 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
135 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
254 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
91 views

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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1answer
111 views

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
90 views

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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1answer
636 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 ...
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2answers
99 views

Moving a marble in a maze using wind force

For a school assignment, I have to write a game where you can move a ball through a maze by generating unidirectional wind when the mouse is clicked. The ball is on a flat surface. The concept is ...
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2answers
1k views

Sound pressure levels: Why doesn't blowing in someone's ear cause hearing damage?

Quoth Wolfram Alpha: 5000 Pascals ≈ 0.51 × lung air pressure that a typical adult human can exert (≈ 9800 Pa) ≈ 50 × sound pressure at the threshold of human pain (≈ 100 Pa) And yet the ...
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2answers
76 views

Room not getting cooled

I am in a room which is heated up duringg day, in night outside temp is quite low, but my room with a ceiling fan running still feels hot as it was in day if I step outside door its cold. There is ...
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1answer
72 views

What happens if I move air at relativistic speeds [closed]

What happens if I accelerate air to the speed of light? To be more specific I'd like to know what will happen if I do the following: some volume of air (just regular atmospheric air), I accelerate it ...
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1answer
92 views

how to get high humidity and low temperature in room [closed]

I want to start mushroom farm for that I have to maintain high humidity and low temperature for that ,So i finding solution for how to get high humidity and low temperature at low cost.
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3answers
4k views

Can air make shadows?

I have read about schlieren photography which uses the ability of non-uniform air to create shadows. Is it really possible that air makes shadows?
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1answer
35 views

Why do the force get bigger as the angle of roof get bigger?

I am doing this experiment at school to find out how the surface area of roof and angle affect on the wind force applied on the roof. My results show that the force gets bigger as the angle and ...
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1answer
62 views

Enclosures & Air Flow

Imagine you have a box, initially fully sealed with an electronic component generating heat. You create a small hole at the bottom and a large hole at the top. What effect does this have on airflow ...
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1answer
98 views

Pressure of air in a cup

If I have a 1.0m long cylindrical cup, and fill it up to $h$ = 0.5m with water, then the 0.5m of air above it will be at atmospheric pressure. But if I now place a perfect seal on the cylinder, and ...
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2answers
80 views

Can I create a car that powered by sound energy?

If I create a car that has an ideal loudspeaker (that can emit sound with any positive real number of amplitude) on car roof then loudspeaker emit very very loud sound (sound may be complex or be ...
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0answers
23 views

How much air does it take to lift the seeds? [closed]

I have a vessel with seed and water in side. The is a total of 6100 Lbs. and water is 523.6 Gals. the bulk density of the seed is 178 Lbs/CuFt. The water seed mix is expected to be 8' above the ...
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1answer
28 views

Thermodynamics question about space height and temperature

Little "discussion" happening at our brewery and I'm hoping to get it answered once and for all. We put in a walk in cooler. Some of us think that making the cooler 10' high will make the contents in ...
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1answer
53 views

If methane is pumped into a room, how does it disperse?

So, if methane (natural gas) is slowly pumped into a room containing regular air, does the methane mix uniformly with the air as soon as it's pumped in (immediately expanding to fill it's container), ...
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2answers
253 views

buoyancy of compressed air as discussed in a previous thread [closed]

i was reading a previously locked thread about the compressed air from tires in the movie transporter three, and the writer asked if compressed air is heavier than regular and therefore does not float....
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1answer
62 views

Relation between Temperature and Pressure inside a bottle in a room?

I have an empty bottle with no cap in my room, so it is supposed to be filled with air. I made the air warm inside the bottle by dropping an igniting matchstick inside the bottle. Warm air will rise ...
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1answer
143 views

Is it easier to lift an object in air rather than in vacuum?

I was reading about why lifting an object in water is easier then in air. The explanation goes on the line that the water which was above the object will fall downward and sideways, taking the place ...
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2answers
58 views

If I'm using a compressor typically used for powering nail guns and other tools, why can't I make the air colder when I release it?

I've always been fascinated in learning how to make liquid air, and I learned that there is a branch called physical chemistry, which deals in the manufacturing of different chemicals. My question is, ...
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0answers
44 views

how to influence RH and air presure to resistance of air

For example higher RH (relative humidity of air) provide lower air electrical resistance. But how I can calculate with this relation? Moreover air pressure (between 1500 and 500 hpa) can influence ...
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0answers
32 views

Is it possible to retreive energy from the air displaced by a moving car?

Correct me if I'm wrong : When a car is moving it creates an over pressure on the front and a lower pressure on the back. So, from the point of view of the car, the air hitting the windshield has to ...
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1answer
26 views

Airfoil down force measurement

I have an airfoil connected to two supporting uprights, and each upright has a load cell to the front and to the back, between the bottom of the uprights and a test mount surface. From this system I ...
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2answers
94 views

Is the air we breathe ionized?

Is the air we breathe ionized? I am reading a book that says that the air we breathe is ionized but from what I have read so far, it is only the air in the upper atmosphere that is ionized.