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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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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946 views

Tube under water and air pressure

If you take apart a syringe you are left with one piece that is a tube with a tiny hole in one end and the open end of a tube at the other. If you then submerge this underwater and cover the small ...
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1answer
47 views

Different density objects falling on Earth's atmosphere?

So I finally understood why 2 objects with different masses, free falling from the same distance reach Earth's surface at the same time (due to the objects Inertia). Now when the objects fall in the ...
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1answer
19 views

Ostwald gas solubility for air-sea gas exchange of O2

The bubble-mediated component of the air-sea gas exchange can be parameterized with Woolf's (1997) formula as: $$ K_{b} = W \frac{2450}{\beta_{0} \left( 1 + \frac{1}{\left( ...
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1answer
43 views

Is there an equivalent to wetness for air?

I was wondering if there was something equivalent to the property of being wet with water, but with air instead. For example, if I drop water on my shirt, I'll notice by its appearance and feel that ...
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31 views

Which is the most accurate way to model the fundamental atmospheric parameters of the Earth?

I need to calculate the fundamental atmospheric parameters, I mean the actual ones, this is not an exercise but a model for a real world application so I need to take account of the humidity of air. I ...
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1answer
176 views

Pressure vs Volume Calculation for air

I have 1 litre of air in a sealed container at atmosphere pressure (approx 15 psi absolute). I want to reduce pressure in the container by 1 psi ( 14 psi absolute or -1 psig). If I understand ...
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55 views

What kinds of reactions happen when bubbling air through water?

Mostly I have seen air bubbling used to remove impurities in the water itself, like exemplified in this course packet. This is called "Sparging," but I have yet to learn much about transfer between ...
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33 views

Cost vs. purity producing liquid oxygen [closed]

We are a group of rocket amatures who build rockets using LOX and ethanol as propellent. We normally buy the LOX from supplier. But lately we have been discussing if there is an easy way to produce it ...
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56 views

Closed pipe/sound resonance sound type sound coming from mineral processing plant

I work near a very large mineral processing plant which does vibrate our building and there is also a sound/feeling very similar to the closed pipe/sound resonance that is achieved when opening a back ...
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1answer
159 views

May I know how a vortex tube works? [duplicate]

From my point of view, high gas pressure input creates air rotation inside the tube. Due to the rotation, the kinetic energy in the air change to internal energy. The internal energy release as heat ...
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31 views

Remote control wireless helicopter hovering in cruising aircraft, will it move the aircraft with stability [duplicate]

A Mini Toy Helicopter is left for hovering inside the cabin of an Aircraft, while the aircraft is cruising at the speed of 900 Km/h. Helicopter has no contact with the surface of the aircraft. The ...
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2answers
157 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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193 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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3answers
2k views

If hydrogen and helium are lighter than air, why won't liquid hydrogen and liquid helium defy gravity?

Title says it all. If hydrogen and helium are lighter than air, why won't liquid hydrogen and liquid helium defy gravity?
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143 views

The Ultimate Hand Dryer

I have come across many hand dryers that attempt to dry your hands really fast after you wash them. Here are two of them: XLERATOR http://www.exceldryer.com/ Dyson Airblade ...
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2answers
2k views

Speed of a fly inside a car

A couple of weeks ago I was travelling in a car (120 km/h approximately) and I saw a fly flying in front of me (inside the car, near my nose, windows closed). I wonder how was that possible. Does it ...
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192 views

Train motion… Push or Pull?

While arguing against my friend today about the turbulence appearing between train's wheels. I told that the train pushes air aside during its motion through the tracks. But, he rejected it. Then, ...
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565 views

Is it reasonable for a heavy door to “open by itself” (ie from differences in air pressure) if it had already been slightly ajar?

If you consider a basically uniform massive door (say, 300 N) where there is some coefficient $\mu_{s,k}$ of static and kinetic friction between the thing on the inside of the door, and where the ...
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3answers
232 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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2answers
81 views

Why does my eardrum feel strange inside a car?

When I was riding a car (I was not the driver), my eardrum felt a little similar to the case when I was in a plane that was taking off, and little loss of hearing. Nothing was played inside. The ...
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1answer
80 views

Viability of Dysons bladeless fans? [closed]

Do Dyson's bladeless fans produce enough air pressure to cool say an air conditioning unit and do they produce a vortex pressure like a bladed fan?
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1answer
151 views

If a balloon is continuously filled with air and stays at a constant shape and size will there be any empty space in the balloon?

If a container like a balloon but with constant volume is filled, is it possible to pack air molecules so closely together that they don't have any empty space between them? If so, what would this ...
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201 views

What mechanisms exist for generating lift on a static object?

What mechanisms exist for generating lift on a static object? Condition is: Other than propellers I know that generating lift on a static object in a sense of anti-gravity for e.g. drone is not ...
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2answers
510 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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4answers
91 views

Can the weight of a bird be measured, considering air friction? [duplicate]

Assume that a bird of mass 1.5 kg is held in a box at height 500m and this setup is placed on a weighing machine. Now, the bird starts to hover in the box pushing the air downwards, and is at a ...
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99 views

Is air resistance affected by both mass and surface area?

If so, which has the biggest impact?
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2k views

Why do particles in high pressure air always flow to lower pressure?

The title really says it all: Why is this case? A "Feynman type" answer would be really appreciated as I'm more of a layman that a physicist.
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1answer
508 views

Which one conducts heat better: water, or air?

If we were to assume room temperature of 20C, which of the fluids conducts heat better, and why?
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2answers
94 views

Simulate free fall in a rotating torus?

Say I have a rotating torus filled with air at 1 atmospheric pressure at sufficient speed (and inclined along the direction of the force of gravity with respect to Earth). If the rotation speed were ...
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1answer
253 views

Speed of sound in air

Quick question. I thought that the speed of sound in air was constant, say in the right conditions of pressure and temperature, and humidity... 300 m/s. Now, if I have a sound source that moves ...
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1answer
166 views

What caused Simon Faithfull's chair to fall appart?

There is an art/science video clip on youtube, by Simon Faithful, called Escape Vehicle no.6 (chair in space). It shows a simple steel office chair, tied to a weather balloon, ascending into the upper ...
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1answer
65 views

If I take a bottle of air into space, and open it, then close it and come back to earth and open it one last time, what would happen?

I was reading this post, but no one seem to go further as say what would happen if you brought the bottle back to Earth? Guess what another thing I'm wanting got know is, what would now be in the ...
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31 views

About using screw in air compression and air Engine [closed]

I want to use screw to build compressed air engine, as following image As I designed, this screw rotate in a tube My Question is: How successful this idea? Note: If this question not related to ...
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3answers
55 views

How would filling a milk canister with helium affect the reading it makes on a scale?

Let's say that if I put a milk canister on a scale it shows 10kg. If I fill it with Helium it must necessarily be less than this, right? Can someone explain this (probably trivial) thing to me? :) ...
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1answer
29 views

Can low end hepa vaccums still clean near all of the air?

In the US HEPA filters will remove 99.97% of particles sized 0.3 microns. In Europe HEPA filters do not have to meet this exact figure and there are different classes of HEPA filters e.g. h10(removes ...
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1answer
26 views

Change in volume of air held at the top of a tube with upper end closed and holding some liquid [closed]

Consider a tube both end open.dip one end in a container with water..close the top with your thumb..(make sure some air remains between your thumb and the liquid in the tube)..now take the tube out of ...
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1answer
999 views

HEPA vs. water filter in vacuum cleaning [closed]

What is the difference between air being filtered with HEPA or water? Which one performs better within a non-allergic home environment? Does water filter have a meaning still when common vacuum ...
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2answers
178 views

Weighing a flying bird [duplicate]

Let thing of a bird standing still in a box on top of a weighing machine that shows a mass $m_0$. Now, imagine that the bird is flying, still in the same box and the same weighing machine shows a mass ...
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2answers
494 views

Why do we feel a sudden chill?

When we are in a room, especially in some old houses, we feel this sudden rush of cold air. How does a strong air current arise and pass away so quickly?(lasts for about a second) I know air-currents ...
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2answers
222 views

Supermarket refrigerator - why is it noticebable colder in this shop area?

As we know fridge can't cool room in which it is (according to Second Law of Thermodynamics, heat emitted by fridge is greater than heat absorped). However, when we go next to the fridge in ...
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1answer
216 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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0answers
16 views

Loud, low-frequency “booming” sound in car [duplicate]

I drive a Scion XD, and I've noticed that whenever I drive at about 40mi/hr or so with just the back windows rolled down, I get a loud "booming" effect at roughly 10Hz. What causes this? I assume it ...
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0answers
22 views

Need more details on How to Make a Water Bottle Cap Pop Off With Air Pressure [closed]

i have been assigned the topic air pressure in physics presentations,so i decided to do the above experiment but the teacher has asked for a technical report on the experiment.I am a bit confused on ...
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10 views

Particle Velocity and Air Velocity

Is the any relationship (equation) between particle velocity and air velocity? Is it possible to determine the air velocity from particle velocity?
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2answers
58 views

Why do cold drinks get sweaty?

I drink a lot of iced tea and live in a very humid part of the country. My drink accumulates so much water, I had to purchase coasters to collect all the water dripping from the sides. Where does ...
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0answers
36 views

How to calculate how much air is leaking out of an object?

I have a pressurated pvc pipe. I am wondering how long it would take for it to leak out on a small tube. I really just want to know how to do the equation, so I could figure it out depending on the ...
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1answer
24 views

What could be added to tap water to reduce air bubble formation on a submerged object?

Submerge your hand in a bucket of water. Some air bubbles appear immediately and others add to the surface of the hand over time. Is there anything that could be added to the water to reduce the ...
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23 views

Relative humidity of an air parcel with decreasing temperature

I'm a bit confused while doing relative humidity calculations. To make the case simple: let's say I have my room temperature at 25 degrees with a 50% relative humidity (RH). If I take an air parcel ...
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Is the density of air in the mountains higher at the equator?

I have heard that at e.g. 5000 m altitude, the subjective feeling is better in the Himalayas than e.g. Tien Shan, because Himalayas are located near the equator, and due to Earth's rotation "air is ...