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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Why does air remain a mixture?

As we all know, air consists of many gases including oxygen and carbon dioxide. I found that carbon dioxide is heavier than O2. Does the volume difference neglect the mass difference? Is it same for ...
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103 views

Density and statistical models for visible air dust

If a laser beam is looked at from the side versus a dark background, a sparkling effect can be seen caused by dust particles in the air hit by the beam. Is there any simple model or coarse ...
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Why the breath sometimes warm and sometimes cold? (2 different explanations!)

If you blow air against your hand with your mouth open, you feel warm breath. If you do with with your lips closed except for a small opening, you feel cold breath. One explanation from here says ...
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Direction of rotation of a celing fan

From Constellation Energy Quick energy efficiency tip: To stay cool and manage your energy at the same time, use ceiling fans to create a “wind chill” in rooms you are using. The wind chill ...
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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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2answers
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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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689 views

At what g is terminal velocity not terminal?

How weak would gravity need to be in order for a human to reliably survive the terminal velocity of falling through air? (Context: watching scifi on a space station with a variety of artificial ...
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2answers
627 views

The measurement of $g$ and air resistance

Suppose I am trying to determine the value of the acceleration due to gravity by simply dropping objects from a ledge. If I did not account for air resistance, would the acceleration due to gravity ...
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1answer
105 views

How do we describe the relationship of balloon size and related lift?

We know that hydrogen and helium are lighter that air. Therefore it is certain that they would create a lifting force when enclosed in a balloon. How do we describe the relationship of balloon size ...
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What is the roaring in a roaring fire?

I was just starting a barbecue fire by blowing on the smouldering coals when I realised I had no idea what the sound was actually caused by. I can make the sound by blowing at almost any flame I can ...
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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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5answers
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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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Is there an upper frequency limit to ultrasound?

Wikipedia has this diagram of the acoustic frequency spectrum: Is there an upper limit to the frequencies you can transmit through the air? Are they absorbed more and more at higher frequencies, ...
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59 views

How do I determine when this object is about to get covered in dew? I can measure the environment parameters

There is a large disk of glass sitting outside, it is pretty thick and wide. Via different sensors hooked up to a controller, I can measure the air temperature, glass temperature (on the surface), and ...
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19k views

Do salt lamps really produce negative ions?

Do salt lamps really produce negative ions? Do you know about any scientific study that could support this assertion or disprove it?
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1answer
793 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 ...
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7answers
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Does it take significantly more fuel to fly a heavier airplane?

I was reading in the papers how some-airline-or-the-other increased their prices for extra luggage, citing increased fuel costs. Now I'm a bit skeptical. Using the (wrong) Bernoulli-effect ...
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1answer
757 views

Local Mach number for an airfoil

I would like to know how to calculate the local Mach number on the upper surface of an airfoil given the ambient temperature, the local velocity on the airfoil surface, the freestream velocity, and ...
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2answers
182 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 ...
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3answers
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How does the Dyson air multiplier fan create negative pressure?

I'm curious as to how the Dyson air multiplier fan works. So far I understand that it creates negative air pressure that causes air behind and around the device to be sucked into the air stream and ...
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1answer
116 views

Clouds in closed hydrosphere

Is possible estimate the needed size of an geodesic dome (like in the Eden project) for creating an real hydrosphere - especially clouds (and rain)? With other words, under what circumstances can ...
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How did Enrico Fermi calculate the classical Fermi Problem?

From Wikipedia: Fermi was known for his ability to make good approximate calculations with little or no actual data, hence the name. One example is his estimate of the strength of the atomic bomb ...
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1answer
310 views

How to calculate pressure at altitude when there is 0 temperature lapse?

To calculate pressure at a given altitude, the following formula is used: $p = p_0 \cdot \left(1 - \frac{L \cdot h}{T_0} \right)^\frac{g \cdot M}{R \cdot L}$ (the values can be found here) This ...
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2answers
367 views

Horizontal Speed of Descending Parachute

I understand how to get the vertical (descent speed) of a parachute and its payload, but how could one find the horizontal speed/velocity of this parachute depending on the speed of the wind? (yeah I ...
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1answer
136 views

Air simulation environment [closed]

I will preface this with the fact that I am not a physicist...I am an engineer by trade. I am working on a research problem that will involve flight of an organism with varying shapes, and I am ...
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1answer
727 views

How does a V formation save fuel for the lead plane?

I'm watching an episode of Mythbusters where they show aircraft saving 3-5% fuel when flying in a tight V formation. Interestingly, this also applies for the lead airplane. How is that possible for ...
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1answer
337 views

Fluid Dynamics: Bernoulli Air Tunnel

I have the following question as part of a lab intro to explain the more complicated stuff I'l actually have to submit in the lab. I put all the questions here just to show my thought pattern/what ...
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The visibility of air

For pilots of gliders or sailplanes, the 'thermal' is the most important phenomena of the air. A thermal is classically described as an upward flow of air caused by ground level heating of air that ...
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1answer
212 views

Can i use coils with compressed air to make a superconductor?

What im saying is inside pipes i am going to use compressing so that that in the places with low pressure they cool the superconducotor. is this possible? Can i use this concept to make ...
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1answer
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Air flow coming out of a fan feels much stronger than air flow coming in. Why? [duplicate]

Possible Duplicate: Why is exhaling more forceful than inhaling? If I put my hand behind my computer's system block, I can feel a very strong flux of air coming out, as it is being pushed ...
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0answers
209 views

How do I find the acceleration of an object at a certain velocity if I know it's mass and terminal velocity? [closed]

I have a mass of 85kg and a terminal velocity of 46.7m/s. I think I correctly calculated the coefficient of air resistance(b) as 17.84 because I know that the Resistance force at terminal velocity is ...
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1answer
550 views

What kind of curve would describe the rate of air coming out of a balloon?

If one graphed the volume per time of air being expelled from a common elastic balloon out of a hole of constant size relative to the balloon's surface area, would the curve of the graph be ...
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3answers
5k views

Function of air conditioner

What i always thought that air conditioners blow the cool air without knowing that they actually take the warm air from indoor and from outdoor. But whats the point of taking air from indoor and ...
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3answers
2k views

Can smoke stay still in the air?

Can a small amount of smoke be dense enough to stay in the air keeping its shape for a minute or so? Or does it always dissipate quickly? If not smoke, can anything else stay in the air for a minute ...
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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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Why would colder air disperse condensation on a car windshield?

The outside temperature was somewhere between the hot and cold that blows on the inside through the car's vents. I know the condensate is on my side because I can reach forward and write on it with my ...
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Can pockets of air exist underwater?

If yes, why don't they fill up with water, and can you breathe the air there? Like, it's not exactly atmosphere there, but an underwater cave with higher ceiling. P.S. Possible that it has a ...
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3answers
142 views

Are there convective movements similar to those in clouds everywhere in the atmosphere?

I heard there were powerful convective movements in clouds which were responsible for increasing the size of water droplets or ice crystals. My question is: do the same movements appear outside of ...
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1answer
334 views

A flying fly inside a sealed box on a scale

suppose there is a scale able to measure weight with an uncertainty of $10^{-9}kg$ . On the scale, an airtight plastic chamber is placed. Initially, a fly of mass $10^{-5}kg$ is sitting at the bottom ...
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3answers
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How air humidity affects dry process of a washing?

I've noticed that during wet weather my washing does not want to dry. Is it because of lower temperature, or because of air humidity?
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2answers
851 views

What is the terminal velocity for a mobile phone

You may have seen the story of the iPhone which was dropped from perhaps 13,500 feet by a skydiver - it survived. This made me wonder how to work out the terminal velocity for something like that. ...
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3answers
271 views

What is the volume of a parcel of air of a giving weight at average sea level pressure

I know this is probably some basic math once you have the figures, but my Google-fu is failing me. Say I have 5 pounds of air. Air meaning, the typical composition of the atmosphere of Earth. And by ...
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Air Regeneration in Closed Systems

I wonder what's the way to regenerate O2 in air without using consumable chemicals (where one can use electricity through electrolisis or using UV lamps)? We can dissolve water into O2 & H2, but ...
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3answers
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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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1answer
222 views

What is it that makes this structure cause turbulence?

I'm trying to design a quasi-simple vertical axis wind turbine, and a coworker came up with this design to focus the wind as it reaches the turbine in a wind tunnel. He says that there's going to be ...
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3answers
788 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
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Ozone Hole in the South Pole

Perhaps this should be a chemistry question, but it seems to have physics attributes. There's a perennial ozone "hole" around the south pole created by destruction from Cl based chemicals like CFCs. ...
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1answer
158 views

What's the name for taking pictures of air flow in a normal room?

There is a way to photograph air in a room. It makes convection, breathing and movement visible. The result looks a bit like a soap bubble. This is some kind of optical effect. No special gases or ...
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462 views

Burning alcohol vapor

Let's imagine a plastic container, sealed closed. We fill half of it with alcohol, then we generate a spark. The question is: can the mixture of alcohol and air burn, or do we need a hole to let air ...
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Is it possible for wind to break the sound barrier?

I understand that in nature wind would never get high enough, but I am just curious as to whether physics would allow this to occur or not.