The atmosphere of Earth is the layer of gases, commonly known as air, retained by Earth's gravity, surrounding the planet Earth and forming its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).
By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases.
Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude, and air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere and in artificial atmospheres.
Earth's atmosphere has changed much since its formation as primarily a hydrogen atmosphere, and has changed dramatically on several occasions—for example, the Great Oxidation Event 2.4 billion years ago, greatly increased oxygen in the atmosphere from practically no oxygen to levels closer to present day. Humans have also contributed to significant changes in atmospheric composition through air pollution, especially since industrialisation, leading to rapid environmental change such as ozone depletion and global warming.
The atmosphere has a mass of about 5.15×1018 kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km (62 mi), or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km (75 mi). Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition.
The study of Earth's atmosphere and its processes is called atmospheric science (aerology), and includes multiple subfields, such as climatology and atmospheric physics. Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The study of historic atmosphere is called paleoclimatology.
I saw on a web page a video of tiny Agnes Scott College vs Princeton University from 1966 on GE College Bowl.Agnes Scott won (!), but one of the questions that both schools got wrong was
asked by the moderator:
The speed of sound in air is about 1,100 feet/sec. The speed of sound in steel is...
Hi everyone
I'm new around here and I wonder if anyone can help please. I'm taking hot air off the chimney stack inside a factory at a temperature ranging between 700 and 400 degrees going through a 4 inch stainless steel pipe with 3mm wall thickness. This pipe line will be about 35 meters long...
hi all,
i would like to set up a small lab experiment to try to create visible "terrestrial scintillation", whereby one can see fluctuations in air density (turbulent air), like the rear of the jet in this image:
i have sketched a small setup before i begin; the test will send a projected...
Hey everyone,I am trying to make a helicopter using an AVR or ARDUINO BOARD I wanted to know how do I calculate the force required to lift the helicopter.Can anyone also help me how much revolutions per minute(r.p.m) should the fans generate.I am planning to use two fans.
Homework Statement
A car tire has a volume of 10 L and is inflated to a gauge pressure of 30 psi (207,000 Pa) at 20°C. How many air molecules are there inside the tire?Homework Equations
N = PV/ kbT
The Attempt at a Solution
(207,000 Pa )x (0.01 m3) / (1.38 x 10^-21 x 293) =5.12 x 10^23...
I would like to know how exactly or if the velocity of air molecules affect the light i.e electromagnetic waves passing through it. Ignoring the effect of pressure and/or temperature differences in the air which might also affect the light (due to changes in refractive index).
Hey, everyone
I just bought an air purifier yesterday (the Honeywell 50250 model) and have a question about whether or not it's normal what is happening when I turn it on. I followed the instructions exactly in terms of assembly (it was really only putting on the pre-filter - no other assembly...
My wife and some of my friends have been experiencing a spike in moderate allergy symptoms (Sx) this past week or two, and I was wondering if adding a HEPA air purifier at home in our bedroom would help. This recent PF thread discussed air purifiers, but not really from an allergy perspective...
Hello all, I want to say thank you in advance for any and all advice on my question. My classical mechanics textbook (Marion Thornton) has been taking me through motion for a particle with retarding forces.
The example it keeps giving is:
m dv/dt = -kmv
which can be solved for:
v = v0e-kt...
Yes compressing air increase its temperature but does that necessarily increase pressure? In an pellet gun a spring driven piston compresses the air which increases the temperature but wouldn't any increasing pressure simply retard the piston's advance? Because the chamber volume is not fixed...
Hi,
I'm an instructor at an online school, and my text says
“ Air pressure is the amount of pressure the atmosphere places on the surface of Earth. Air pressure is usually measured as the weight of the column of air above a square meter (N/m2). As altitude increases, air density decreases and...
Looking to do a experiment on the effects of air resistance training on the body.
doing basic exercises such as jogging push ups. Maybe a couple of curls ;).got facility design herewondering what your thoughts and opinions on this would be.
I"ve seen several texts that say something like this:
Our equation of motion along x is
dvx/dt = -g(vx/vt)
Integrating this, we obtain equation 178 at this link (pretty near the top; sorry, but I can't figure out how to put the equation here). It's from FitzPatrick's online notes for...
Homework Statement
Air consists of approximately 78% Nitrogen in volume, 21% Oxygen and 1% Argon. The atomic weight of Nitrogen is approximately 14, that of Oxygen 16, and that of Argon 40.
Nitrogen occupies air in weight by
(1) (a) 76% (b) 77% (c)78% (d)79%
Homework EquationsThe...
A large tank filled with air is compressed to 49 PSI. A valve is open and air escapes through the hole (d = 0.04 ft) to the atmosphere. How long will it take for the compressed air to reach 29 PSI.
Assume constant temperature.
Not exactly sure how to approach this problem since the flow rate...
I had a helium balloon in my car tied so it hangs down by string toughing nothing. Windows are rolled up. Heat and AC are off. Air inside the car is not moving and car is parked with motor running. When I step on the gas pedal and car takes off forward balloon goes forward towards the...
The air conditioner is set up to put the temperature at 72F. Which I hate because that's cold, but whatever. The air conditioner turns on and works for about 6 minutes when it automatically turns off because the temperature reached 72F. It stays off for 10 minutes and then it turns on again...
If a pulse of light, which has momentum p = E/c, interacts with particles of air, would it not change their momentum over time, causing mechanical energy (sound)?
As I understand it, sound is mechanical energy moving through particles as they vibrate. Why can't the momentum of a pulse of light...
I would like to receive some input about this "equation" formulated by me, a=f(i), regarding a system with a permanent magnet and an air core coil acting as an electromagnet, as described in the image:
I understand that the acceleration provided to the toy car will be a function of the...
Homework Statement
Air is drawn into a compressor at normal temperature and pressure (NTP) and compressed to a pressure of 6 bar gauge. After compression the air is delivered at 1.2m^3/min and cooled to a temperature of 30C, at which point condensate is collected at the rate of 2 litres per...
Hello,
I am currently doing research on the aerodynamic properties of a rotating cylinder in a cylindrical housing.
The cylinder represents a rotor in a electric motor. The air gap between rotor and stator is about 0.5mm.
I'm looking for a theoretical analysis and calculation on the...
Homework Statement
We are using a device(as shown in the image) to blow air into a 200L plastic barrel. We want to know how much air (volume) that is needed to raise the anchor from the seabed.
Homework EquationsThe Attempt at a Solution
The anchor will start moving upwards when the sum of...
So I'm trying to figure out what kind of energy that I can expect out of a few different setups.
Here are the barrel bore diameters.
.224
.308
.5
.77
The barrels are usually rifles and some projectiles are full size (size of bore) while others use sabot's where a .224 or .308 can be shot...
I've had some mold in my shower and even my car this past year (long story, but I HIGHLY suspect my car mechanic caused it, by leaving a nasty greasy residue on my fibers...).
I also have allergies and eczema. :frown: They causes itchy rashes (though usually very manageable by avoiding...
Homework Statement
Air consists of a approximately 78% Nitrogen in volume,21% Oxygen and 1% Argon. The atomic weight of Nitrogen is 14, that of Oxygen 16 and that of Argon 40
(1) Nitrogen occupies air in weight by
(a) 76% (b) 77% (c) 78% (d) 79%
Homework EquationsThe Attempt at a Solution
I...
mass of air X velocity = mass of man x gravity
(10000)x(v)=60x10
velocity=600/10000
how come velocity is so less?
I am still in school so forgive me if my calculations look stupid.
How do I find out gauss from air core inductor 36mohm pumped with ~130amps 9ms long?
http://www.parts-express.com/erse-25mh-14-awg-perfect-layer-inductor-crossover-coil--266-380
Greatly appriciated.
I'm looking to see how much the dielectric constant of air will change mostly as a function or air temperature.
Is there a formula that outputs air dielectric as a function of temperature or atmospheric pressure?
I have noted three different phenomena due to high electric fields in air.
1. When I run a ten-stage voltage multiplier I get sparking and crackling.
2. When I run the multiplier but current limit the output with ten 720k resistors in series, I get a violet arc that is sometimes smooth and...
Recently, the inverter ACs have become quite famous. I got to know that in inverter ACs, the compressor is never actually switched off. The compressor speed is varied in accordance with the temperature of the room. This keeps the room temperature constant, unlike the previous technologies, where...
Hi, I have a airbottle of 30bar pressure, 1000lit.From the airbottle I had made a line of 25 nb and fitted a pressure reducing valve in the line with set pressure 5bar.I am interested to know the flowrate in the line. Please help
I am a contractor. I install water lines. Once installed we have to pressure test them. We pump the lines up to 150 PSI of water. If the PSI drops one of 2 things is wrong, either i have a leak in the line, or there is a small amount of air in the line. Generally if it is air, it stabilizes...
Homework Statement
From a previous post in this forum, unfortunately the thread is closed for answers otherwise I would have posted it there: https://www.physicsforums.com/threads/thermodynamic-filling-of-tank-matlab.479112/
A 70 ft3 rigid insulated tank contains air at 14.7 psia and 80 º F...
Hi, I have a question about air flow. My room is located on the corner-end of my building, on the 7th floor. I have two windows, each one facing a different side of the building, and one of the windows typically produces the breeze, and the other never does.
When the door to my room is closed...
Wondering if I have a sealed steel tank filled with air and the air temp is 0C and the air pressure in the tank is 0, then heat is applied to the tank - what will the pressure be 100C? At 200C? At 300C? I assume the rate of expansion is constant, but correct me if this is wrong. Thanks.
Homework Statement
An EM wave from air enters a medium.
The electric fields are
--> ^
E1 = E01 cos(2πv(z/c-t) x
--> ^
E2 =E02cos(k(2z-ct)x in a medium ,where the wave number k and frequency v refer to their value in air.the medium...
Hello,
I don't know how to compute that number, but probably is a kind of reference value...
Q: How many ion-pairs are there in normal conditions* in the air?
(This is not homework, it is just out of curiosity.)
Thank you for your time.
Regards,
ORF
* 1 atm, 300K.
I'm working on a project involving compressing air to a desired high pressure. So far the only equation I've been paying attention to is the ideal gas law. My question is if an air compressor pump is rated to create a maximum pressure of 100 psi based on its inlet being at atmospheric pressure...
Homework Statement
Let's say, P = 1.00 atm
and T =273K
and density of air at STP = 1.29 g/L
Homework EquationsThe Attempt at a Solution
I'm not too sure...
PV = nRT
n = PV/RT
= P/RT = 1/(0.0821*273) *1.29 g/L ?
Although I have seen values such as 3 kV/mm for the dielectric breakdown of air, I was curious if there was an analytical or semi-analytical model of the ionization of say N2 under a uniform electric field. I am aware of Peek's law. Am I correct in assuming it is empirical? How might one connect...
Homework Statement
(a) Explain how heat is lost from a hot surface to the surrounding air.
The Attempt at a Solution
We will assume as there has been no other stipulation that the effect of radiation is negligible and thus we are taking purely about conduction.
We will also assume as there...
What is wrong here. If I double speed drag will be 4 times higher. The engine needs to put out approximately 4 times more power. Energy consumption will be 4 time higher for a specific time period. However if it is a fixed distance I will arrive in half the time an the energy consumption will...
Homework Statement
Homework Equations
Equations posted in pictures attached
The Attempt at a Solution
I haven't attempted it yet because I am confused about something. If the-cv^2 case is for objects that hit terminal velocity at the fastest rate, why are my graphs showing that I should use...
Hi.
If I fill a glass with water up to the top and close it with a coaster, I can turn it upside down without the coaster falling off and spilling everything. Usually, this is explained with the atmospheric air pressure being bigger than the pressure of the water inside the glass (hence, it...
Methanotrophs already exist in most soils. If we expose them to more methane, will they eat more? A solar powered fan blowing air down a tube that ran along under soil, with lots of small holes along its length - would that reduce the methane in the air?
As a second part to the question, does...
A smooth flexible tube 1mm in diameter and 1 foot in length holds air at normal / atmospheric pressure (14.7psi).
the tube is open at one end. the other end is connected to a tank by an open valve.
the tube is peristaltically compressed so all the air in the tube is forced into the tank.
the...
Homework Statement
(a) A parallel plate capacitor has area A = 1 cm2, a plate separation of d = 0.01m, and is filled with air. If the breakdown field is E0 = 3 × 106V/m, calculate the maximum voltage and charge the capacitor can hold.
Homework Equations
dielectric constant of air = 1
Q=CV...