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
706 views
Speed of a fly inside a car
A couple of weeks ago I was travelling in a car (120 km/h approximately) and I saw a fly flying in front of me (inside the car, near my nose, windows closed). I wonder how was that possible.
Does it ...
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6answers
1k views
Why is air invisible?
I think that something is invisible if it's isolated particles are smaller than the wavelength of visible light. Is this correct?
Why is air invisible? What about other gases and fumes which are ...
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votes
2answers
244 views
Sum total distance of electrons on a spherical surface
What is the sum total distance between every possible pair of point charges when there are n point charges on a spherical surface?
All point charges can only and are located on the infinitesimal ...
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4answers
677 views
Why is exhaling more forceful than inhaling?
By blowing at pencil, a piece of paper, or another object up to fifty centimeters away, I can cause it to move away from me significantly. But I can't move an object toward myself by inhaling sharply ...
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votes
2answers
639 views
How can sound waves propagate through air?
We know that the sound waves propagate through air, and it can't travel through vacuum. so the thing that help it doing that is the air's molecules pressure. So my question how can that happens? I ...
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3answers
557 views
Maxiumum weight a buoy can float [closed]
I have a buoy that can hold 2943.02 cubic millimeters of non-pressurized air, I need and equation to work out the maximum weight that the buoy can float.
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4answers
6k views
Why does the air we blow/exhale out from our mouths change from hot to cold depending on the size of the opening we make with our mouth?
Why does the air we blow/exhale out from our mouths change from hot to cold depending on the size of the opening we make with our mouth?
It's not just a subtle difference, but significant in my ...
3
votes
2answers
546 views
How air humidity affects how much time is needed for heating the air?
In cold weathers it is suggested to put a humidifier since the air gets too dry. I wonder how the humidity affects how much time is needed to get the air at a temperature of 20 Celsius degrees? I mean ...
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5answers
2k views
If I take a bottle of air into space, and open it, where does it go?
It seems to me that space doesn't have any/much air, and if my bottle is full of air, when I open it, where does the air go?
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1answer
267 views
wind vs air resistance
I'm wondering which offers more resistance: pulling an object at some speed through air, or holding the object steady against wind at the same speed.
I think initially people would think same ...
4
votes
5answers
632 views
What principles does an air glider use?
I just saw this video which was kind of nifty. What principles govern this? Is it simply that 700 lbs of air pressure are exerted from that little 1 HP blower? What would you have to take into ...
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votes
2answers
518 views
Is the wind's force on a stationary object proportional to $v^2$?
I am on a boat docked at Cape Charles, VA, about 30 or 40 miles from the center of Hurricane Irene. This understandably got me thinking about the force of wind on the boat. Since air friction is ...
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votes
3answers
368 views
How would you move without gravity?
I'm wondering how would you move without gravity? You would still have air pressure at 1Atm.
Would you "swim" in the air or would you have do something else?
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3answers
257 views
Why does air remain a mixture?
As we all know, air consists of many gases including oxygen and carbon dioxyde. I found that Carbon dioxyde is heavier then O2. Does the volume difference neglect the mass difference? Is it same for ...
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vote
1answer
168 views
Difference in vertical stratification of partial pressure due to gravity
Say you have a mixture of two ideal gases in the presence of gravity. There is a vertical pressure gradient on the mixture due to the force balance. This condition is required to prevent the entire ...
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vote
2answers
91 views
Amount of material required for a pressure tank
I read the answer for the question Why is a hot air balloon “stiff”? and thought something sounded ridiculous. My engineering requirement is that the walls be strong enough. Here $T$ will be the ...
