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.

learn more… | top users | synonyms

3
votes
4answers
12k views

What is the difference between air pressure and atmospheric pressure?

I know that air pressure and temperature are inversely proportional. Now I saw in a book that "Atmospheric pressure decreases as we go higher and higher." But at greater heights the temperature ...
3
votes
2answers
12k views

Sound - what happens with the particles when a wave passes

I'm having some problems in understanding the principles of sound propagation. The wave propagates though air (for example) exerts compression, which is followed by rarefaction. I think I got than ...
3
votes
3answers
148 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 ...
3
votes
2answers
312 views

Paradox while Cooling & Heating in Air? [duplicate]

I was thinking about how asteroids get "burned" up in the upper atmosphere as they approach the earth surface due to the atmosphere of earth heating the asteroids immensely as a result of air ...
3
votes
2answers
913 views

Beryllium Vacuum Sphere Boat/Aircraft

Is it possible to make a solid rigid evacuated "balloon" out of Beryllium or other elements or alloys? The critical buckling pressure at which an evacuated sphere is given as $$ P_1=\frac{2E\cdot\...
3
votes
2answers
141 views

Does a scale weigh a bee flying inside a box?

This question is very similar to this one or even this one except some minor differences. The box is much larger than the bee. The box has no top cover. The bee is flying still in the middle of the ...
3
votes
4answers
326 views

Can we have air flow without air noise?

I want to have air flow in my room, but I don't want a fan to move the air because of the air noise. I think the noise comes from all air molecules going to the same direction. If I can move the air ...
3
votes
2answers
743 views

How is a vacuum formed and measured by this pneumatics attachment?

Please excuse me if this question is misplaced and also for my narrow understanding of physics. Firstly, I'm asking simply because the robot I've now been set to work with uses an air pneumatics ...
3
votes
1answer
74 views

Why would air try to escape from under a pot?

I put a wet Calphalon pot down flat on a wet synthetic countertop. None of the surfaces or liquids was hot. Bubbles started appearing a second or two later from under the rim of the pot in one area. (...
3
votes
2answers
63 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, ...
3
votes
3answers
748 views

Does launching a rocket in lower density air require more or less fuel?

Given two environments that are identical, except for air density (e.g. Cape Canaveral, but at Mount Everest's height), would launching a rocket require more or less fuel at the lower air density?
3
votes
1answer
209 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 ...
3
votes
2answers
230 views

Why is a material such as plastic air-tight?

I'm not too familiar with fluid mechanics, but i always wondered how let's say plastic containers would be able to contain a fluid, such as gas or water. How does plastic prevent the molecules of the ...
3
votes
2answers
1k views

Why did they used to make the mill chimneys so tall?

Why did they used to make the mill chimneys so tall? This question was asked in an Engineering Interview at Cambridge University.
3
votes
1answer
384 views

Conditions of applicability of potential flow about an airfoil

In many cases the flow about an airfoil is calculated by solving the Laplace equation, (for example in the Hess-Smith panel method). If the velocity field is irrotational and its divergence its zero, ...
3
votes
1answer
353 views

Influence of air resistance in space

Consider the following situation: You are locked inside a cylindric container allowing you to move around freely without being in contact with any of the items or surfaces aboard. The container is ...
3
votes
1answer
688 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 ...
3
votes
3answers
1k 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?
3
votes
4answers
502 views

Is a turbine the same thing as a motor?

Is a turbine the same thing as a motor? We know that water, wind and nuclear power plants rotate a turbine so is this turbine like a motor? I think we can generate electricity by rotating a motor too. ...
3
votes
1answer
2k views

Why is my breath hot when i open my mouth all the way, but cold if I blow like a whistle? [duplicate]

I observed this as when I want to cool my soup I blow like a whistle and when I want to warm my hands I open my mouth more as my breath is warmer now.
3
votes
1answer
886 views

Why I can't feel the difference of atmospheric pressure between a closed room and outside?

As far as I know atmospheric pressure is the result of the weight of earth's atmosphere. It has an approximate value of $10^5 Nm^{-2}$. Then why I can't feel it? My physics teacher told me that we are ...
3
votes
2answers
382 views

air flow with line fans

I must vent air through an 8 inch duct from one area to another using an 8 inch line fan. One goal is to vent the maximum amount of air possible through the duct. Is there any different between ...
3
votes
2answers
73 views

Does Coriolis effect affect snowing?

Right now, outside is snowing. No matter what window I look from, the snow constantly for last few hours tends to fall to the right close to the window, and to the left close to the building across ...
3
votes
1answer
868 views

How to Calculate temperature, given speed of sound and relative humidity?

I know the solution in reverse direction, but I find it very complex to go the other way around and calculate the temperature when given the speed of sound and relative humidity, any ideas?
3
votes
1answer
168 views

How big an egg can be? [closed]

Please hold on to flag as off-topic. Few days ago I received a question - how big an egg can possibly big? Can it be as big as 1 meter, as a human? (Imagining that there could be really huge animals ...
3
votes
1answer
918 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 ...
3
votes
1answer
128 views

Repel air by electrostatic charge

It is known that an electrostatically charged object can repel or attract a flow of water. Can this also apply to an air flow? And if so, would it happen only due to the humidity via water molecules, ...
3
votes
1answer
214 views

Air nozzle outlet profile efficiency, concave/convex

I need to design a contracting nozzle for air. The application is quite simple, consider it like an hair dryer but the flow speed is even lower. So the Mach number is very low and the flow laminar. If ...
3
votes
2answers
119 views

Stability of planet-enclosing shell supported by atmosphere

I understand that a hollow spherical shell of uniform density gives net zero gravitational attraction to objects inside it. So in vacuum, a ball at the centre of a spherical shell would not be stable ...
3
votes
1answer
629 views

Static pressure of free air stream

One of the common misunderstandings regarding Bernoulli's principle is that, in general, "faster moving air has lower pressure". Bernoulli's principle can only be applied to asingle streamline in ...
3
votes
1answer
346 views

How should holes in a Tesla turbine look like?

I think of building a Tesla turbine out of old hard drives. Now I wonder how to cut ventilation holes in the platters. On the internet there are a lot of different attempts on that matter. A lot of ...
3
votes
1answer
402 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 I'm ...
3
votes
0answers
49 views

Behaviour of Altimeter at different temperatures

I have realized that the Altimeter of my bike computer (it uses Air Pressure to determine altitude and needs to be calibrated every start) is not consistent at different temperatures. At the Start ...
3
votes
0answers
68 views

Bottle cap burst phenomenon [closed]

There is a trick you can do with a simple plastic water bottle: After putting the cap on as tight as you can, you twist the body of the bottle a few times so that it compresses the air in the bottle. ...
3
votes
3answers
313 views

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. ...
2
votes
2answers
282 views

Why is a hole in a ball?

I wanted to know why there is a hole in the ball (basketball, volleyball, handball) to fill the ball with air. Why can't the ball come with filled in air and fully sealed so that there is no loss of ...
2
votes
2answers
1k views

Do we hear sounds differently on the highest mountains?

Some searching gives that above 6,000 meter altitude the air density is less than half of that at sea level. Speed of sound is about 15-20% slower and "acoustic impedance" seems to change too. Do ...
2
votes
2answers
533 views

Fluid Dynamics - Water Bottle Drink Mix: Air or No Air?

If you take an ordinary sized plastic water bottle full of water and pour a packet of powdered (or liquid) drink mix into it, Will shaking the bottle with the cap screwed on to dissolve the mix into ...
2
votes
2answers
138 views

Could one make steel balloons? [duplicate]

Reading this question reminded me of an idea I once had, and I wonder whether it's feasible. Imagine a hollow ball made of something strong, like steel. Imagine there is nothing inside; only vacuum. ...
2
votes
2answers
4k 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 can'...
2
votes
3answers
90 views

How does inhalation work?

In school, we learn that during inhalation, the diaphragm expands, causing air to get sucked into our lungs. You can feel this suction by putting your hand over your mouth while inhaling. Why is that?...
2
votes
3answers
128 views

How can Denver offer Hot Air Balloon rides?

So the air density in Denver is 1.0 kg/m^3. And heated air has the density of 0.95 kg/m^3. So adding the weight of the basket and balloon I don't understand how a hot air balloon could get off the ...
2
votes
2answers
34k 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?
2
votes
2answers
347 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 ...
2
votes
2answers
120 views

Mathematics of simplified air resistance

I recently encountered a problem in which when throwing a ball upwards one has to determine whether it goes up or comes down faster when not only was gravity to be considered, but also air resistance ...
2
votes
1answer
141 views

Can sound frequency create more ideal conditions for fire?

You may have seen the recent story of a device that engineers claim can extinguish flames using sound frequency. An older article loosely explains the theory behind how this works: Sound travels ...
2
votes
1answer
2k views

how does air pressure affect the speed of sound

How does air pressure affect the speed of sound in relation to its kinetic theory etc? I have tried searching this but i have not found a suitable answer as other websites simply related to air ...
2
votes
1answer
694 views

Vortex Air Intake

Why is a vortex air intake in an engine cause the fuel to burn more efficiently within a vehicle. Why is this more efficient.
2
votes
3answers
2k views

How could electromagnetic waves propagate through space although they have no electrons?

How could electric fields in these waves propagate through space although in space there's no electrons for the electric field to be formed? is there another type of charged particles that carry the ...
2
votes
1answer
201 views

Whirlwind/tornado/dust devil in the middle of nowhere

I live in area which have many properties similar to desert. Many times when I drive by I see a whirlwind/tornado/dust devil of sand or other garbage parts. I would like to ask how this was normally ...