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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2answers
30 views

Non-popping bubbles

I used a compressed air can to clean my laptop's keyboard and speakers. After that procedure I noticed there're small bubbles in the holes of the speakers. I've tried to pop them with a thin brush and ...
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Does “wind speed” depend on the density of air?

Our intuitive notion of "wind speed" is that it is the speed at which air molecules are moving at point. Consider two situations where the velocity of the air molecules are the same but the ...
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Room Pressure and Tiny Gaps

First of all, how can atmospheric pressure be same in a closed room when it clearly depend on the height of the air column. Compared to atmosphere, the room few metres high so how can air pressure be ...
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1answer
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What if speed of air exceeds 340m/s?

We know that Mach cones are formed when an object moves faster than the speed of sound. This creates huge noise in the surroundings. Here the airplane is moving faster than sound relative to ...
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How high would a half deflated ballon float outside of a third floor?

this a question that has been haunting me for many years now. If I have a half deflated helium baloon that floats one meter above the ground on a third floor and I take it outside, will it float one ...
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Could a hot-air balloon fly if the temperature outside is hotter than inside?

If a hot-air balloon was approaching an active volcano where the air temperature outside was presumably much hotter than the air inside the balloon itself, would it start to fall into the volcano or ...
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Why can we neglect the force of air (atmosphere) acting on the body in free-body diagram?

Let's say we have a body at rest. The forces acting on this body are: gravitational force and normal force. The pressure of the air is $1bar = 100kPa $ and lets assume that the surface of the ...
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Air density at very high altitudes ( $h > 100 km $)

The temperature gradient model works very well for altitudes as high as a few kilometers above sea level. However such a model is obviously wrong at high altitudes as temperature starts to rise rather ...
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What happens if two parallel square plates approach each other in a gas?

Imagine two solid massive parallel square plates, each with side length $l$ and mass $m$, approaching each other along the line that connects their centers of mass. At the moment we look at them they ...
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1answer
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Is there a little less oxygen (I mean less by density) in the equator than at the poles? [closed]

Since gravity is a little greater at the poles, does that mean there's also more oxygen there in the atmosphere? I'm asking about the atmospheric density of the oxygen, whether there'd be more oxygen ...
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How can a butterfly dodge the windshield of a fast moving car?

While driving, an unlucky butterfly was about to hit my windshield. But instead of splattering, it sort of glided smoothly upwards across the surface of my windshield. The butterfly was clearly not ...
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Is the buoyant force of air implicitly neglected for an object half-inmersed in water?

I saw in this answer that the atmospheric pressure is conveniently canceled mathematically when taking the atmospheric pressure at the level of the top of the object. However, when I was inventing ...
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1answer
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Creating a Bouyancy Force Generator

How much energy is needed to maintain boiling water? (I'm assuming $1400~\rm W$). With that said, when air is added to an object to decrease its density, does the strength of its buoyant force ...
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Trying to find force relative to change in air pressure of a bag

Let us say I put an object covered in paint on an airbag and assume that the object won't roll around on the bag, the bag won't stretch or pop, and the temperature is constant. I'm also measuring the ...
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Can you ionise air via thermionic emission of electrons?

Assuming air is made up only of 78% $N_2$ and 22% $O_2$, what percentage of the $N_2$ and $O_2$ would gain a negative charge if held in a container with a high density of free electrons?
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How determine flow rate of air into a sealed vessel with increasing pressure

I am able to measure a target pressure inside the vessel or rate of increasing pressure, temperature and know th volume of the vessel (1000L). I would like to determine flow rate of air from a ...
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Is it true that a pair of open windows create a strong continuous “draft” wind?

A common belief is that opening two windows or doors inside the home can create a strong and steady flow of air (a "draft") that a single window would not create. This seems somewhat ...
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How to increase the air pressure of an air pump? [closed]

How do we increase the air pressure of an air pump or aerator? In an aquarium shop, I saw a setup like the photo shown below, where in the low pressure air is given as input through a thin inlet pipe, ...
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How would a small desk fan improve the air flow of a room?

Say one were sitting in a room with poor ventilation. If wind doesn't rebound off of surfaces, how would a small desk fan alter the airflow of the room?
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Does the pressure change in the air blower if the outstream pipe get smaller?

I'm having this thinking, let's assume that I have an air blower and I have a gauge set at the very first point of the outstream pipe, my question what happens to the pressure at the gauge point if ...
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3answers
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Does air move faster between rooms with higher temperature differences? [closed]

A pair of rooms at an identical temperature. A pair of rooms where one is very hot and the other very cold. Does air move faster between one pair of rooms than the other? If it does, is that what ...
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Why does air pressure decrease with altitude?

I am looking to find the reason: why air pressure decreases with altitude? Has it to do with the fact that gravitational force is less at higher altitude due to the greater distance between the masses?...
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1answer
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What happens to the bubbles in this CPU thermal paste? (video)

I've been studying the best method to apply thermal paste and currently thinking the spread method might seem best where you spread an even thin layer across the whole CPU and then apply the heat sink,...
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How does the dielectric breakdown of air change with Temperature, Humidity and Pressure?

I've done a lot of online research but the results I've found are't great, and sometimes even contradict each other. Are you aware of any paper describing this change? Starting from wiki, that ...
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What's the terminal velocity for an air bubble in water?

If you release an air bubble sufficiently far under the surface of water, what is the terminal velocity of the bubble that is created? Is the terminal velocity contant or varying (the size of the ...
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1answer
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What might cause water vapor to move against the flow of air in an enclosed space?

I have a rectangular tent that I'm planning to use as a mushroom fruiting chamber. It measures approximately 120 x 60 x 150 cm and has two duct fans installed--an intake fan near the top of the left ...
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1answer
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What is the formula to calculate the amount of water in the air at a certain temperature and relative humidity?

I'm trying to find a formula that will give me as a result, the amount of water in a cubic meter of air. I have read this question How to calculate the volume of water in a certain amount of air, ...
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Calculating dew point, which air temperature should I use (inside vent or outside)?

I'm trying to make my air quality sensor resistant to dew. This air quality sensor has vent with fan, which doesn't "like" to have dew inside. My idea is to use heater and connect it to this ...
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1answer
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Why does lighter air goes up? [duplicate]

If we increase the temperature of a volume of air it will rise up but if we look from molecular level, there kinetic energy has just changed but not thier weight so why they rise up and do not go in ...
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1answer
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Will $α$ particles be absorbed in air?

From internet resources, $α$ particles can only travel few distance in air (or few range in air), is that because it been absorbed in air?
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Suction cup on car dashboard

I have this suction cup to hold dashcam in car. When I leave car in sun suction fails and camera falls down. Did camera fall because air got heated under suction and expanded or plastic/rubber ...
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1answer
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Bernoulli Equation and Continuity Equation for Air Flow

In textbooks, Bernoulli Equation and Continuity Equation are typically used with Fluids. It's unclear how they can be applied to air flows. Once thing I noticed is that since $\rho$ is very small for ...
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Can a glass cup be used to collect positively-charged air ions from the Earth's atmosphere?

I am wondering if the positively-charged air ions that are descending down from Earth's Ionosphere can be collected using a glass cup. Since a glass cup will allow an electric field to pass through it,...
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Why do two similar objects not hit the ground at different times?

The formula for air resistance is $$F_{air}=\frac{1}{2}\rho cAv^2 $$ where $\rho$ is the density of the air, $c$ is the drag coefficient, $A$ is the cross sectional area of the object and $v$ is the ...
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1answer
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Pool cover efficiency of absorbing and retaining heat in pool water

Looking into the options of adding and retaining heat in the outdoor pool (and saving wallet) - heat inverter, roof solar water heater, gas heaters etc. the pool cover seems to rule them all (at least ...
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3answers
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Ceiling fans with just one large winglet? [closed]

I am from India and in India ceiling fans have generally three wings. Today while laying on my bed a question came in my mind. First of all, I know that if we use just a single wing at a time of same ...
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Amount and percentage of water in air

I was wondering about the relationship between the amount of water in the air, and the percentage. Is the following correct? Let's take an example of 20⁰C. According to this page air at that ...
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Does fog help clean the air of dangerous levels of smoke particles after a major wildfire?

I am currently in the area of three major wildfires happening in Oregon. Our air quality is 995 at the moment (which is beyond hazardous to breathe and is seeping into our houses). This morning we ...
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Does an overcast sky alter the sound waves coming from above it (like the sound of an airplane)?

This morning, in our little backyard, I heard an airplane that was flying above the clouds, which were completely and uniformly covering the blue sky, as if they formed one big homogeneous grey mass. ...
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What causes the Coandă effect? [duplicate]

What causes the Coandă effect? Here's my understanding of it: When a fluid flows around a curved surface it has high velocity and so low pressure its pressure will be lower than the atmospheric ...
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1answer
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How much can water compress air?

So I was thinking of using a barometric sensor to measure the compression of air in a tube in order to measure water level in a tank (Basic diagram below). So based on the equation $ \frac{P_1 V_1}{...
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2answers
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Filling Pressurised Cartridge with valve?

I have a standart compressor rated up to 8 bars, using it for painting, cleaning, pumping up wheels, etc. I now want to make a little backyard project, essentially a super-powered super soaker, which ...
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1answer
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Does the fermentation of batter increase its weight?

Indian dishes like the Idli and the Dosa are prepared from a fermented batter composed of mainly rice and black grams. (See here for more information on the preparation.) Would the fermentation ...
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Does aerogel “blow up” in a vacuum?

Discussions in comments below How can aerogel be lighter than air? really make an answer to this important. The conclusions there are that aerogel could in some cases be "lighter than air" ...
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How can aerogel be lighter than air?

Air has a density of about $\mathrm{1.3 kg/m^3}$. From Carbon aerogels by Marcus A. Worsley and Theodore F. Baumann: Though silica aerogels held the title of "world's lightest material" for ...
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Why do air compressors have separate inlets/outlets?

Our fridge recently broke down, and now I'd like to turn the leftover compressor into an air compressor. I've also got an old tank from a water pump. This one has only 1 opening. All the air ...
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1answer
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Is atmospheric pressure balanced on an object as it moves?

Consider a box sliding along a friction-less floor at a constant velocity. Now typically atmospheric pressure is 14.7 psi on all surfaces of the object. But if it is moving at a constant velocity, ...
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What is the opposite of explosive decompression?

Is it something like "implosive compression"? Cannot find the correct term. Explosive decompression is when the pressure rapidly drops, e.g. spaceship gets a hole and passengers cannot ...
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2answers
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Why has warm air a higher water saturation than cold air?

I've wondered about that for a while but all I read is commonly just "Warm/hot air has a higher energy so when it hits the surface of a liquid, it has a higher probability to transfer energy, ...
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1answer
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Can a Bouyant bottle in water lift an identical bottle full of water outside of water [closed]

Imagine you have 2, 5 Litre bottles. One of them is full of air at normal air pressure and is submerged at the bottom of a 5m tube full of water. The submerged bottle has a piece of string hanging ...

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