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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If an unsealed water bottle has three holes at a different heights, why would the lower hole give out the most water? Is it because of air pressure?

If an unsealed water bottle has three holes at a different heights, why would the lower hole give out the most water? Is it because of air pressure? I am guessing it's because air pressure pushed on ...
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0answers
6 views

What liquid has the lowest known solubility of O2 at 20°C, 1 atm?

I have recently started a project on hydropneumatic devices, i.e. devices that use hydraulic fluids in conjunction with high pressure gases. In such systems, the most immediate thing you would want ...
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0answers
11 views

Excitation of air with the eigen-frequency

I was just wondering (as a layman) what the eigenfrequency of breathable air is? If it exists: what would be the effects of exciting air with its eigenfrequency (w/ regard to humans, matter nearby?)
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0answers
18 views

How heated air moves [closed]

Ok so how does air move when heated up inside a tube or cone? I am working on a wood stove and curious on how I can get air to flow faster or easier into the burn chambers to fuel the wood. Heat ...
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2answers
33 views

Density of air using ideal gas law

I need to find the density of air using (I think) the ideal gas law. I have calculated $V$ of an ideal gas at s.t.p. to be $.0224m^3$. I am asked to find the density of air knowing it's temperature ...
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1answer
25 views

What is the temperature of compress air entering the atmosphere?

Hi to all of you enthusiasts, I have a 1 liter compressed air tank with around 207 bar of air pressure inside. It has been sitting out for a while and I am assuming its temperature has almost reached ...
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0answers
28 views

What amount of force could be created by a person “swimming” in air?

Had a question on a physics test, a person is at rest on a frictionless surface and can not throw anything, can they move? I said yes, by "swimming" against the air and got docked because "it ...
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3answers
181 views

The speed of air rising through a heated tube

I would like to get an explanations of an observed physical phenomena. When a metal tube is placed vertically and heated and the air inside rises, the speed of the air moving through the tube ...
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0answers
14 views

power of an engine with wind

I know the power of an engine to overcome air drag is $1/2 c_d ρAv^3$. If the speed of the car $25\ \mathrm{m s}^{-1}$ (relative to the ground) and it travels in opposite direction to a wind at a ...
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0answers
25 views

What exactly is Breakdown Voltage of Air?

Most of the online sources say that the breakdown voltage of air is 30kV/cm. I've made a Cockcroft Walton multiplier and I can see the air breaking in between 17-18kV/cm. Only in a discussion at one ...
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2answers
40 views

Atmospheric pressure

What is the significance of atmospheric pressure being referenced as 100 kPa ? Does that really mean 10000 kg/m$^2$ acting upon us ? If we are measuring only collision force on the surface and not ...
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3answers
38 views

Wind restistance as function of temperature

Is temperature-dependent wind resistance the reason there's a significant increase in fuel consumption in my Prius car when air temperature drops by 30 degrees K from 300 degrees K? I think I see a ...
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1answer
996 views

How fast would an object have to move to create a vacuum behind it?

When an object moves, I assume that the air above it, instead of remaining at the same general height, is pulled downward as it is passed in order to fill the low-pressure area behind the object where ...
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1answer
36 views

Why does the composition of the air does not change with altitude?

Air contains about 78% nitrogen and 21% oxygen independent of altitude (up to 100 km). Why is this? Shouldn't the concentration of nitrogen increase with higher altitudes since nitrogen has a lower ...
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0answers
29 views

How can air pollution contribute towards light pollution?

I was just wondering if air pollutants such as soot, could reflect light into the night sky, and thus be a potential source of light pollution. If that's true, can you please suggest any other air ...
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7answers
3k 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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0answers
18 views

Calculating optimal heat dissipation/air-flow out-of/into an enclosure - hole size vs number of holes

I am not sure if this is the right place to ask, but I figured it would be a physics question. Essentially I have an enclosure that I will be using to house the components to build a computer. I am ...
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2answers
57 views

Rising glass in xkcd what if

In http://what-if.xkcd.com/6/, Around this time, the glass on the left starts to visibly lift into the air. The air pressure is trying to squeeze the glass and water together. This is the ...
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2answers
59 views

When I open a window to air out the room, how does the smell disperse?

Let's say I'm in a room with some kind of noxious stink, possibly of flatulent nature. The quickest way to right the world that comes to mind is to open a window. When I open a window, how do the ...
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1answer
56 views

Water vs. Air : Heat Absorption/Capacity

I am not a physicist by any means and not even a current student, but nonetheless I am looking for an answer. Here is what I have gotten so far from university websites and other various resources on ...
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0answers
17 views

Affect of temperature and pressure on humidity

If the temperature outside is 0°C and the air is fully saturated, when I heat the air to 21°C without adding any water the relative humidity inside the house would be a very dry 25%. The dewpoint does ...
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4answers
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5answers
12k views

Why do heavier objects fall faster in air?

We all know that in an idealised world all objects accelerate at the same rate when dropped regardless of their mass. We also know that in reality (or more accurately, in air) a lead feather falls ...
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1answer
44 views

How fitting is the sound wave (transverse wave) propagation model? (for the layman)

Air is a gas, then how is sound wave propagation possible? I mean, gas particles have a tendency to travel in a straight line, so how does a sound wave occur via compression and rarefaction? Most ...
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3answers
134 views

Free Fall with Air Resistance

Can somebody help me understanding why when free falling the force on the vertical axis is F= -mg-kv, where k is the constant of air resistance and v the velocity? Suppose the vertical axis is ...
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1answer
111 views

If my windows are open on a windy day, the curtains sway and the doors slam shut. Why don't I feel this wind?

I am standing indoors, right in front of my open window, as I see my curtains moving back and forth and I can hear my closed doors shaking. I can also hear the wind howling loudly. Why don't I feel ...
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45 views

Parachute Model

Can you tell me if this model is correct or not? [assuming drag is linearly proportional to the velocity] Considering y-axis vertical and x-axis horizontal,with y positive upwards: 1) ...
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1answer
47 views

Force felt by parachutist when opening the parachute [closed]

When falling down with air resistance, y-axis vertical (positive is up), x-axis is horizontal, we have that: $F_y=-mg-kv=ma_y$, where $k$ is the drag coefficient. Now if the man opens the parachute, ...
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2answers
47 views

Can wind be defined as momentum/mass of air molecules?

In the past I thought a breeze of wind was "made" from a large amount of air molecules going all the same direction in the same speed. But it's not like that, actually this voted answer, this site, ...
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1answer
42 views

Forces in a body falling with air resistance

I would like to know why when a body falls with air resistance, we have that the drag caused by the air is -kv and the acceleration is -mg. What I don't understand is how they both have the same sign ...
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1answer
2k views

Paper plane between two fans - is this possible?

The setup: two fans facing each other, distance around 1m. Both are turned on. In between them, place a simple paper plane and according to this video, it will fly. ...
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3answers
71 views

Kitchen physics question I should know.

I don't know anything about physics so this may sound dumb. I punctured a hole on the top of a condensed milk can to drizzle on my snow cone, but when I tried to poor it it barely came out. I randomly ...
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1answer
59 views

Is it easier or harder to move moist air with a fan?

From what I understand, the molecular weight of water is lower than the molecular weight of nitrogen and oxygen. So, shouldn't it be easier for a fan to move moist air than dry air of the same ...
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2answers
105 views

If I Blow smoke out my window, will any come inside my room?

My girlfriend and I have got into a lively debate about whether or not my flatmates can smell the smoke I blow out my window. Can you help us? Here is the scenario. The smoker, places himself ...
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1answer
22 views

Does moving air suck in air from left and right of its path? [closed]

When air is made to move (e.g. by a fan) it has a lower pressure than when it is still. Essentially, this moving air should become a low pressure zone relative to the static air around it and the ...
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1answer
34 views

How do buoyancy control devices (BCD) work?

I get that having more air decreases density and increases buoyancy. However, we can take the diver-BCD-oxygen-tank to be a single system. How can the pumping of air from the tank into a vest around ...
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2answers
97 views

volume of the air bubble in the water

How does the depth affect the volume (the radius) of an air bubble in the water, if the temperature and density of the water are constant. Is there any relation combining this? Can I say that ...
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5answers
4k views

What makes water heavier than air?

I apologize in advance if this is too basic for this site. Considering that hydrogen is lighter then oxygen, and water is 2/3 hydrogen, and only 1/3 oxygen, and our "air" is comprised mainly of ...
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0answers
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How to restict air flow without reducing pressure

I have a large volume of lightly pressurized air say 10000 cubic feet at 1 psi above atmospheric pressure. I want to move it to another area through a duct which is 20 in by 20 in. Airflow will be ...
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1answer
56 views

Is liquid “air” (nitrogen, oxygen, aragon mixture) flammable?

I was wondering if liquid "air" (nitrogen, oxygen, and argon mixture) was flammable. Imagine you have a container. This container contains liquid air. The air is in liquid form, and is in direct ...
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2answers
42 views

Objects and forces: air resistance

A force always works between two objects. When we are talking about air resistance acting on a skydiver for example, would air be considered the second objects besides the skydiver?
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0answers
45 views

Can 1km diameter ball of water preserve it's integrity before hitting the ground falling from 10km altitude?

I still argue with my friend over some big ball of water (1km in diameter) that is being instantly created 10km over the surface of the earth in perfect sphere form. I stated, that as it hit the Earth ...
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2answers
50 views

How does the pressure inside car tyre change once the car is lifted/ put back on the ground? [duplicate]

Imagine a car on a jack; how does the pressure change once the car is lifted (all wheels in air - not touching the ground). I'd be interested in knowing whether the pressure will increase or decrease ...
2
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2answers
202 views

Are raindrops actually “shaped like tears” when they fall?

Raindrops are always pictured like this, people imagine they have this shape when they fall, but is this true? Doesn't this shape create too much drag? What shape do they really have? It would also be ...
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0answers
57 views

When does $PV = const$ stop being true?

My problem is the following: a 15-liters cylinder contains air compressed at 370 bar. How many liter will flow out of the cylinder once uncompressed at 1 bar? I thought that I could use $PV = const$ ...
4
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1answer
47 views

Is single tree shadow locally affecting air temperature?

In other words, is the air temperature under a single tree different from a couple meters away, in a hot day and under the sun? There are several effects potentially interacting: Tree transpiration ...
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1answer
48 views

What is the effect of constant wind on a hot air balloon?

If a hot air balloon is being carried by a continuous wind current in a particular direction, in which direction will the flags on its basket wave?
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0answers
26 views

Why does individual N2 molecule rise when heated?

I get that hot air is less dense so it rises due to floatation and all, but what happens to one individual diatomic Nitrogen that it increases it's distance from ground? And why is it that the air is ...
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0answers
14 views

Simulating pneumatic tools/devices?

I need to simulate an air compressor/pneumatic system for a train simulator. How do I find the pressure of an air tank after lots of things have used small portions of the compressed air? For ...
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4answers
445 views

Why does moving air have low pressure?

According to Wikipedia lift in an aircraft is due to an area of low pressure formed above the wings of an aircraft due to the fast moving air there. So why exactly is an area of low pressure created ...