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.
711
questions
0
votes
2
answers
45
views
Does EM wave lose energy in air?
Light is EM wave.
As it travels through vacuum, it does not lose energy but I am wondering if it travels in air, just imagine light in your home. Before it reaches your eye, it has to travel through ...
- 236
17
votes
3
answers
2k
views
Would an adhesive surface have more air resistance?
Imagine spreading double-sticky tape all over the surface of a car or a plane. Would there more significantly more aerodynamic drag as a result of the adhesive 'sticking' to air molecules and slowing ...
- 353
1
vote
1
answer
59
views
What part of my oven should be hottest, top or bottom? [closed]
My oven has the heating element in the bottom. So the bottom shelf is more directly exposed to it, and should be the hottest shelf.
But hot air rises, so the top shelf should have the hottest air, and ...
- 2,835
2
votes
4
answers
184
views
What is the physical reason for why hot air holds more water vapour, and how does this relate to saturation vapour pressure?
It is said that hot air holds more water vapour.
I guess this means that the saturation vapour pressure of water in air increases with temperature. Is this correct?
How can one derive this result? ...
- 347
1
vote
0
answers
34
views
Airflow between two rooms (one hot, one cold) [closed]
Scenario —
It is night time and somewhat cold outside.
Room 1 (Bedroom): The window is slightly creaked open. I have a space heater going on continually heating room 1. One door is closed to the ...
0
votes
2
answers
44
views
Lift and drag forces in parachuting
EDIT: guys, I am not a physicist and it is not my study field, So even if you see my question is silly to be answered, I hope you can give me a clue.
I hope you are doing well.
I have some questions, ...
6
votes
2
answers
64
views
Air pressure at ground level at the equator
At the equator at sea level you are about 17 miles higher up than at the poles ie 17 miles further from the center of the earth. Yet the air is not the same as it would be 17 miles up at a higher ...
0
votes
3
answers
62
views
How can I mathematically model the entrainment of air through a window?
The Problem
Suppose I have an open window with an area $A$, and a uniform wind source (a fan) pointing towards the window, positioned at a distance $s$ away from the window.
At the exit of the fan, ...
- 1
0
votes
1
answer
24
views
Is the sound from a chimney fire the same as the sound caused by a fire inside a fireplace?
For a while now I've been researching the causes of why a fireplace fire makes a roaring sound, and from what I've read, it mostly has to do with the way air rises, creating a vacuum underneath, ...
- 111
0
votes
1
answer
59
views
Does the earth exert centrifugal force on us in air? [closed]
Whether the centrifugal force exerted by earth due to rotation be felt or even applied to us if we were in air ? The landmass rotates with earth so it is exerted on us radially outwards , but that isn'...
- 281
1
vote
1
answer
64
views
Particles in air
This is a strange question.
I can see particles in the air.They are not dust particles. They are smaller than a pin's point, and millions of them exist. If I put a pattern to them, the majority of ...
30
votes
7
answers
7k
views
Why does blowing a whistle in someone's ear damage it more than blowing directly in their ear? Won't the whistle reduce overall energy?
If I blow really hard from a whistle near someone's ear, it'll hurt a lot. But if I blow directly at a person's ear, it won't hurt nearly as much. But shouldn't the whistle (or any other obstruction) ...
- 740
0
votes
0
answers
53
views
Would everything we see be delayed if light slowed down to 1ms?
I don't know much about physics, though it certainly interests me. so I apologize if this is a dumb question, but if we somehow slowed down the speed of light around us. (like we somehow made air have ...
0
votes
1
answer
49
views
Is there any physical explanation for negative extinction coefficient, $k(E)$, over a spectral range of energies?
Measured data for $n(E)$ of air were fitted to equations for $n(E)$ and $k(E)$. The measured data for n(E) spanned 0.734 to 6.702 eV. To obtain fits to the equations for n(E) and k(E) in the absence ...
- 1
0
votes
3
answers
54
views
Feeling of coldness in heights
We know that due to buoyancy the cold air sinks and warm air floats above it due to it being less dense than cold air. Then why do we feel cold as we go to greater heights/hill stations and feel hot ...
- 558
0
votes
0
answers
22
views
What's the pressure of the air around a burning tea light?
When I let a tea light burn in a small room (with an open window so air pressure is clearly atmospheric pressure), what's the pressure of the air around the tea light? In my opinion it's atmopsheric ...
0
votes
0
answers
23
views
How does the slipstream of a falling object affect flying animals near it?
I am the script supervisor for a short film being created by several of my friends. In the script, it specifies that a bird is sucked downward by the passage of a large falling crate. I am now, ...
0
votes
0
answers
23
views
Can pulling a door fast create air movement that causes heart pain, maybe considering weather pressure of 1035 hPa? How does it work?
Flatmate has a habit of using all his strength to open the door of his room, which is on the adjoining corner of mine. I feel like each time the air is pulled. Now it's winter, air pressure 1035 hPa ...
- 71
0
votes
0
answers
57
views
Why is there a vacuum in the upside down glass and card demonstration?
In this Hila Science video on atmospheric pressure (https://www.youtube.com/watch?v=xJHJsA7bYGc&ab_channel=ScienceOnline) from 2:30-3:05, it shows the common demonstration of turning a glass of ...
- 1,074
0
votes
0
answers
24
views
Would it be possible to use a device pumping air out of it to liquify the sand around it?
The question has to do with the demonstration done by Mark Rober when he made a hot tub by releasing air from below the sand upward at a rate that would increase the amount of air between the sand ...
1
vote
0
answers
20
views
Airflow through tube
I have a tube with an inline fan moving 100 cfm (cubic feet per minute). If I add an additional fan in the same tube capable of moving 100 cfm, what would happen? Would I increase my cfm to 200? Would ...
- 11
1
vote
1
answer
31
views
Pressure over time in a tank with variable volume and an orifice
I have a tank whose one side can be moved, so we can change the pressure inside the tank by this movement. (In my main case this ig going to be a sinosoidal movement). We add an orifice to the tank, ...
1
vote
0
answers
45
views
How long will oxygen last in a $3\times 3\times 3 $ meter room for one person? [closed]
Let's assume that the windows and doors are tightly closed.
How can I calculate at what moment I will feel a lack of oxygen and my well-being will worsen?
Can one person completely consume all the ...
1
vote
1
answer
45
views
Can a cold gas be considered as ideal at a very high speed?
Considering a plane flying in the atmosphere, my book uses the perfect gas law $pV=n\bar RT$. Yet, as the plane itself is taken as the reference, the air ($T=-50°C$) has a speed of $800 \ \mathrm{km/h}...
user343933
2
votes
1
answer
49
views
Theoretically, how can you remove friction between surfaces with air?
I know that if there was a way to compress and control air (think air bender) then it can be used to remove friction between two surfaces. A person could just skate on their feet by focusing this ...
- 21
7
votes
4
answers
894
views
Does an open or a closed cage of canaries weigh less when they are in flight? [duplicate]
Okay this is a bit of an old classic, but I don't think I've heard a good reasonable explanation for what happens:
If you put a cage of canaries on a weigh scale and they take off does the scale still ...
- 724
2
votes
1
answer
103
views
Why does light not disperse in air?
I was studying the prism and how and why it disperses light. My teacher told me that in a prism different wavelengths of light have different refractive indexes because the refractive index depends ...
- 33
0
votes
1
answer
31
views
Can a pipe property affect the length of air flow?
Sorry about the bad title, I'm not even sure how to call that so I'm having trouble researching it, but I made a picture.
Let say you blow through a pipe, other than how strong you blow into it, is ...
- 101
0
votes
0
answers
48
views
Strange behavior with candle and bin
In a corner of a room there is a window where there use to be wax and oil candles burning. Just below the candles, there is a bin. There is a lot of soot on the wall and the ceiling, but not over the ...
- 11
0
votes
2
answers
50
views
What makes air exist as a physical yet almost homogeneous mixture with no difference in concentration across regions?
You would think air being a physical mixture there would be changes in N2:O2 molar ratio across regions. But we all breathe more or less same composition of air, right? How come?
- 51
2
votes
2
answers
83
views
When the air can be regard as incompressible and how to get this conclusion?
The air density changes negligibly when the air velocity $<0.3$ Sound velocity, so in this case it can be regarded as incompressible, How to get to this conclusion?
- 21
1
vote
0
answers
26
views
What kind of vacuum would you achieve if you used a compressor in reverse rated at 8 $\rm bar$? (centrifugal, piston or axial if it matters) [closed]
If you used for example a centrifugal compressor that compresses air from an intake of 1bar to 8bar in reverse, what would be the vacuum achieved in mbars? Can a compressor even work with an ...
- 21
0
votes
0
answers
31
views
How do I extrapolate a value of oxygen particles per million from vacuum pressure Pa/torr
If I have a box of 40 $\text{cm}^3$, with ambient pressure and oxygen, how could I extrapolate and bring down the oxygen level to say 500 ppm from an equation such as $1.33 \times 10^{-4}$ Pa ($1 \...
- 21
0
votes
1
answer
24
views
Within close proximity, how much does the atmosphere influence light and thus what we see?
Not sure if this is the best place to ask. Apologies if not.
(Assume this is under generally average conditions)
Say you have an object that is 1 metre in front of you. When you see that object, how ...
- 15
0
votes
1
answer
43
views
The suction and thrust of an aircraft engine
Does only the air sucked in (not the air that is ejected at the back of the engine) by an airliner engine (turbofan engine) causes a thrust forward or in other words pull the engine forward? and why ?
...
0
votes
0
answers
19
views
Estimating the potential for problems caused by thermal expansion of air bubbles
I am interested in the potential for air bubbles in a plastic structure to expand with heat and put pressure on the plastic surrounding the air bubble.
Let's say the plastic structure is formed by ...
- 301
0
votes
1
answer
53
views
Is atmospheric pressure on an object in vertical plane equal to that of horizontal plane? [duplicate]
Suppose there is a cubic object placed at a surface level. Will the atmospheric pressure exerted on the upper surface of it be equal to that of the pressure exerted on its sides?
As far as I know ...
- 588
-2
votes
2
answers
56
views
Filling the empty bottle with hot air
If I were to fill the empty empty bottle with hot air, how can it be done? If I leave the bottle out in the sunny weather, will the bottle fill with hot air?
When I am filling the empty bottle with ...
0
votes
0
answers
27
views
Does the melting point of a plastic powder dictate the formation of air bubbles?
Suppose we have two cylinders of equal dimensions, vertically oriented, that are each filled with a powder of spherical plastic granules. Each cylinder contains powder with an average size of, say 30 ...
- 301
2
votes
3
answers
707
views
What makes longitudinal waves work?
I am quite confused by what makes a wavefront that is part of the compression (line A) turn back towards the rarefaction area. Lets say that the sound is propagating left to right in the image:
What ...
- 185
0
votes
1
answer
37
views
Does it follow that hot air is always replaced by cold air? [closed]
A cylinder contains a powder made up two substances - spherical grains of metal and spherical grains of plastic. In between the grains are voids, so that the cylinder is made up of 75% powder grains ...
- 301
2
votes
1
answer
48
views
Can you make $\rm H_2O$ out of the air with tools anyone has? [closed]
I was just wondering if you could make $\rm H_2O$ out of the air with tools that everyone has?
16
votes
4
answers
8k
views
Why do raindrops look like sticks?
I always thought that raindrops look like this emoji 💧.
But today, I shot it in slow-mo (see on YouTube), and they look more like sticks.
Was it some light effect of my camera, or do they really look ...
- 2,117
0
votes
1
answer
54
views
UV-absorption capability of air
I am looking for an absorption chart for UV light with a wavelength of around 250 nm in air (ambient, no specific preparation). How much of a beam of this light would be absorbed per meter of path ...
0
votes
2
answers
55
views
If you decreased the mass of a planet, but kept the mass of the atmosphere the same, would the air density decrease?
So, I know that atmospheric pressure is a result of both the atmospheric mass and the force of gravity acting on it. If you were to decrease a planet's gravity, but keep the atmospheric mass the same, ...
- 111
-1
votes
1
answer
42
views
Snorkeling vs diving with a breathing cylinder
If diving with 5m snorkeling pipe our lungs would collapse due to 0.5 atm difference, right?
If diving with a cylinder that has air with atmospheric pressure (the pressure our lungs can use), we can ...
- 113
-1
votes
1
answer
43
views
Is it possible make a train moving with less atmospheric friction if a pressurized air shield is applied at its frontal part?
Like the magnetic field blocks radiation particles approaching Earth could a pressurized air pipe at the frontal part of a train block atmosphere that constantly slows down that train? The pipe should ...
- 447
0
votes
2
answers
43
views
Dust Estimation technique
I'm comparing different coating agents for ammonium sulfate fertilizer granules, coating agent is an additive to limit the dust emission, so I have a new coating agent that is lower cost and more ...
- 1
113
votes
4
answers
11k
views
Why do clouds have well-defined boundaries?
Why do cumulus clouds have well defined boundaries? In other words, what are the physical mechanisms that hold a cloud together, as an entity separate from other clouds, that prevent it from spreading,...
- 55.1k
0
votes
0
answers
15
views
Equation for Velocity of air and Pressure difference
Whenever there is a pressure difference, air will flow from the high pressure (area/point) to low pressure (area/point).
I am looking for the equation that relates the velocity of air to the pressure ...
- 1,343