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.

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1answer
71 views

Relation between Temperature and Pressure inside a bottle in a room?

I have an empty bottle with no cap in my room, so it is supposed to be filled with air. I made the air warm inside the bottle by dropping an igniting matchstick inside the bottle. Warm air will rise ...
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168 views

Is it easier to lift an object in air rather than in vacuum?

I was reading about why lifting an object in water is easier then in air. The explanation goes on the line that the water which was above the object will fall downward and sideways, taking the place ...
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If I'm using a compressor typically used for powering nail guns and other tools, why can't I make the air colder when I release it?

I've always been fascinated in learning how to make liquid air, and I learned that there is a branch called physical chemistry, which deals in the manufacturing of different chemicals. My question is, ...
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how to influence RH and air presure to resistance of air

For example higher RH (relative humidity of air) provide lower air electrical resistance. But how I can calculate with this relation? Moreover air pressure (between 1500 and 500 hpa) can influence ...
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Is it possible to retreive energy from the air displaced by a moving car?

Correct me if I'm wrong : When a car is moving it creates an over pressure on the front and a lower pressure on the back. So, from the point of view of the car, the air hitting the windshield has to ...
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26 views

Airfoil down force measurement

I have an airfoil connected to two supporting uprights, and each upright has a load cell to the front and to the back, between the bottom of the uprights and a test mount surface. From this system I ...
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2answers
99 views

Is the air we breathe ionized?

Is the air we breathe ionized? I am reading a book that says that the air we breathe is ionized but from what I have read so far, it is only the air in the upper atmosphere that is ionized.
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95 views

Air coming out of balloon

I have discovered recently that when we have a balloon in a room filled with air, with temperature $T_1$, and then this balloon gets a hole and air is let out, the temperature of the air that comes ...
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82 views

How does a heated object raise the air temperature around it?

When object is heated and the heat source is removed, how long does it take to cool down and how it does it change the air temperature around it. If We know the temperature of the heated object and ...
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Two-photon absorption fluorescence of air

I'm wondering if there are any major constituents of air which are capable of undergoing two-photon absorption and ultimately fluorescing in the visible spectrum. The original wavelengths of the ...
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3answers
2k views

Is there a resonance frequency to air itself?

Obviously a lot of things cause air to vibrate, but does air have an actual resonance frequency?
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Average distance travelled before absorbtion 253 nm photon in air

At first I wanted to use term "Mean free path" in title but I know it means other kinds of interactions too,not just absorbtion.What I really mean is mean free path but only for absorbtion. For ...
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Airplane trails

Some airplanes leave a trail through some regions of sky. This post explains why it is so, but it seems not enough. The trail is said to be made mostly of water which, on a specific altitude, ...
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Tree-like patterns on plastic surfaces [duplicate]

I noticed tree-like patterns on inner surfaces of home appliances plastic bodies. For example, on the lid of air conditioner indoor unit, inside of humidifier, at the bottom of washing machine powder ...
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Water vapour behaviour during hypersonic expansion

I have a question about the behaviour of air with a small mass fraction of water vapour at extremely low pressures and temperatures. I am currently running experiments in a large vacuum facility that ...
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69 views

How long does it take to fill a $100\ \mathrm{m^2}$ room with new air? [closed]

How long does it take to fill a $100\ \mathrm{m^2}$ room with new air. For example. If the room is $100\ \mathrm{m^2}$ room. The window is $1\ \mathrm{m^2}$ and is left open. How long would it take ...
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Propagation speed of air humidity

I'm currently playing with relative air humidity and temperature sensor that makes measurements in my living room once every 60s. When plotted the data on a chart I noticed that spikes and dips of ...
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Understanding air permeation of a material

I am trying to research on acceptable materials to hold an atmosphere inside of a vacuum. Understanding that air will escape at different rates through all materials, I don't know what the property is ...
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2answers
75 views

Air temperature that would cause same rate of heating to human body as a 40°C hot tub

My son was wondering why a 104°F (40°C) hot tub feels so much hotter than a 104° day. I explained the difference between conduction and convection but we started wondering how hot the air would have ...
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1answer
575 views

Fastest way to melt ice cubes in glass of water

I'm in a restaurant and order a glass of water. What I get is about 50% water 50% ice cubes. So, after finishing my water, I'm left with half a glass of ice cubes. I'm in a hurry, so need to leave as ...
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49 views

Question regarding high air pressure on water in a closed cylinder

I am working on a project concerning aquaculture and the elimination of living (live) invasive species being transferred from one location to another. My question is: Suppose you have a air tight ...
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233 views

Total force generated in a pneumatic cylinder-piston with known gap size

Assuming that we have a pneumatic cylinder-piston with arbitrary but known surface area A, a known clarence c, and a known length L. What is the best model to describe the total steady-state force ...
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36 views

If I froze the residual air in a vacuum tube and sent electrons inside, would the air still ionize?

If I froze the tiny amount of residual air(or cooled it to a liquid) in a vacuum tube and sent electrons inside, would the air still ionize? also how many atoms are in a milligram of air(I can find ...
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31 views

How to have high agitation caused by high air flow while heating the same air?

It may not be possible but I am trying to create an environment that has decent air flow for agitation. I want that environment to receive heat though through convection so increasing temperature over ...
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72 views

Why is the air denser at low heights? [duplicate]

I don't know if it applies to all fluids , but why is air denser at lower heights ?
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3answers
668 views

Does Humid Air Rise (neglecting the effects of weather turbulence-for example in a closed environment like a sealed room)

An internet search will find many people claiming that Humid Air (water vapor) rises. However, I am skeptical because if lighter molecules rose then, it follows that the air would be stratified by ...
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Energy needed to pump air through a tube

I have 10 hollow plastic tubes, which may bend, each 10 cm long but with different internal diameters ranging from 2mm, 2.5mm, 3 mm ... upto 6.5mm. I need to pass through them 500ml of room air with ...
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65 views

What actually happens when light encounters air?

Let’s say a green laser is shone onto a target ten meters away. Suppose we look at a photon as it attempts to travel to the target. Please correct my assumptions as needed. Assumptions: 1. It could ...
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1answer
146 views

At which speed an object becomes hotter as it travels through the air? [duplicate]

Imagine we throw a hot pie at somebody's mug. By the time it arrives at destination, it became slightly less hot. Imagine Chelyabinsk meteor enters the atmosphere. It's cold when it enters yet it ...
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734 views

Does less gravity means less air density?

I have actually two different questions that may result in the same answer. The first one : if the Earth would have less gravity, would it result in less air density? The second one : On a ...
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1answer
58 views

What makes air to spin?

The phenomenon is observed in tornadoes where the air spins with a great speed causing so much damage. Can there be any experiment that can be performed to make the air spin in clockwise or ...
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324 views

A empty bottle with no air inside floats? [closed]

This equation shows that an empty bottle with no air or nothing could float, following this law: ...
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2answers
618 views

Can we create a sound wave only rarefactions or only compressions?

We all know that sound waves consists of a rarefaction and a compression, but can we a sound wave consists of only rarefactions or only compression.
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111 views

Measure force produced by air pressure in pipe system with valve

I'm attempting to design a system that uses pressurised air to shoot tennis balls and am struggling to find the right mathematics to calculate the necessary air pressure and volume needed to propel ...
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1answer
1k views

Is it sensible to have a window fan w/ one intake and one exhaust?

Would a fan such as this, with one fan set to intake and the other to exhaust, have the effect of circulating air such that air from the inside is being expelled by one blade while air from the ...
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574 views

How to start a siphon with a tube filled with liquid?

If I have a tube filled with water, whose one end I dip into a container filled with water. If I release the other end will it start a siphon ?
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1answer
2k views

How does air drying actually work (e.g. on clothes)?

I wonder how laundry, which you hang inside or outside on a laundry rack, clothesline or something similiar becomes actually dry. Water turns gaseous at around 100 C° (depends on the sea level of ...
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100 views

Why large excavated holes can create air currents?

My friend shared this post on my wall, but I got doubt: How can a hole like this create air currents which suck helicopterss also? I didn't really understand.
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165 views

Fan vs. Air-conditioning

At the office, we have the air-conditioning turned on like crazy, and we are therefore freezing... The air-conditioning is coming from the roof. My question is: Does putting a fan blowing in the ...
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1answer
29 views

Can thunderstrikes cause any form of wind

Considering that thunderstrikes makes sound, which is a form of movement in the air, it will generate some form of wind as well (following my logic). But can thunderstrikes cause/generate wind? And ...
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350 views

Refractive index in air depending on altitude

For a homework I need to find, in the case of a mirage, why we can model the refractive index as $n(z)=n_0\sqrt{1+kz}$ (k is constant, z is altitude). I found some demonstrations of the mirage ...
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63 views

Can air plasma ions in a fusor fuse?

I know that hydrogen ions will fuse in a fusor but what about air ions? Can air plasma ions in a fusor fuse? https://en.wikipedia.org/wiki/Fusor, if so, under what cicumstances, and how would I ...
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How ionized is the plasma in a Crookes tube

How ionized is the plasma in a Crookes tube, at $10^{−6}$ to $5 \times 10^{−8}$ atmosphere ($7 \times 10^{−4}$ – $4 \times 10^{−5}$ torr or 0.1–0.005 pascal). Under any of these circumstances is it ...
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How does a helicoper auto-rotate? The force of the air pushing on all blades would equal out. Wouldn't it?

So, I was learning about helicopter and how they auto rotate and I learned that when the engine fails the helicopter starts to fall and the air is thrown up at the blades which turns them like a ...
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How to pump a bag in the fastest way? [closed]

I know the airbag utilize the reaction of sodium to make airbag expanded in a short time. Besides this way, is there any way to pump a bag(about tires size) in a short time? Requirement: <0.1s, ...
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533 views

Under water light reflection of air in a cup vs water in a cup

The last time I was on vacation I was drinking on the swimming pool, and after I was finished with the drinks I started playing with the 2 plastic cups I had, and noticed that the air produces a ...
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8k views

Does hot air have high pressure, and does compreesed air have high pressure?

I have hear a lot about high pressure. Sometimes it says that warm air is less dense and has low pressure, but I thought warm air has high pressure. I know that compressed air is going to be hot, so ...
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what is the degree of ionization of glow discharge tube air at various pressures?

From the minimum air pressure to the highest air pressure achievable with glow discharge tubes what is the degrees of ionization associated with them? What is the minimum degree of ionization of glow ...
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How to see wind?

Is there a wavelength of light at which you could see air moving? I was thinking it would be amazing to put on a pair of goggles which enables you to see how air moves around across a landscape, while ...
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What is a safe mass flow rate

In my machine class, the instructor said that if we use compressed air to clean metal of ourselves then we'll actually get hurt because the pressure is too high. I am wondering, What is considered a ...