air ?

[ada@prorider.or]

The composition of air is unchanged until the height of approximately 10.000 m.

this is what evry one teach us !

by why do people say on altitude let say 5000 meters there is less oxygen wich is not

only the pressure is differant

but why people say that?

[Mud]

:crap:

[Serpico]

.
this thread is awesome...http://www.planetsmilies.com/smilies/party/party0051.gif
.

[ada@prorider.or]

if you take the same pressure let say 1.20
you have the same amount of oxygen on 10.000 as on 0 meters



if you take air on zero meters
with density of 1.20 with 20 % humidity 20 degree C
en
density of 1.20 with 90 humidity 20 degree C

wich has a better viscosity?
and
why

[Serpico]

.

[ada@prorider.or]

mud said:

Less molecules as you go higher

agree

but 1 liter air at sea level

has the same amount of all gasses as a the same amount of gasses as at 5 .000 meters

[saab2000]

I know pressure changes but the composition never does. I am not even aware of changes above 10000 meters. Airplanes routinely fly above 10000 meters and this could create an issue if there were a significant change from the 78% nitrogen/21% Oxygen/1% everything else ratio.

PS - We are an odd planet, with flora and fauna requiring a highly explosive and corrosive gas to survive. Just my thoughts on a boring day. Star Trek could never be, where all sorts of species can co-exist at intergalactic conventions (Star Wars is even worse!!) where they all breathe the same gas and speak English together.

Some types of these things probably require gaseous Mercury or something like that or swim in a composition of something other than dihydrogen oxide.

Geeks and nerds of the world unite.

Sorry for the rambling....... :D

Cees - What brought about your question?:D

[catulle]

I've seen quiet a few people very sick at 3,000mts in Quito, Ecuador. Why? As far as I know, after a certain altitude the body produces more red cells in order to better transport oxygen to the cells of the body (the brain being, in some cases, a part of the body). I mean, is there or isn't there the same amount of oxygen at sea level than at 3,000mts? Hey, I must know. And if there is, what produces "soroche"? Soroche is an old Inca word for the symptoms experienced at altitude.

Now you got me thinking, which is a hell of an accomplishment. So, please, set the record straight.

[saab2000]

The pressure of the air at 3000 meters is less than at sea level, and fairly significantly less. I guess that means there is less air, and therefore less oxygen. What matters is the so-called "Partial Pressure". The ability of the lungs to process the oxygen atoms needed is less at low pressure than at high pressure.

I am not elegant on speaking/writing of these matters, but I know in my own head what I am talking about.

On the airplane we have oxygen masks which will provide enough pressure to survive a depressurization at 41,000 feet. (Whether anyone would be conscious long enough to don the mask is another issue.....)

Maybe a chemist can speak about the gas laws and how they apply. Gas will expand to fill an available volume. At higher altitude there is less gas, therefor less pressure.

[catulle]

The pressure of the air at 3000 meters is less than at sea level, and fairly significantly less. I guess that means there is less air, and therefore less oxygen. What matters is the so-called "Partial Pressure". The ability of the lungs to process the oxygen atoms needed is less at low pressure than at high pressure.

I am not elegant on speaking/writing of these matters, but I know in my own head what I am talking about.

On the airplane we have oxygen masks which will provide enough pressure to survive a depressurization at 41,000 feet. (Whether anyone would be conscious long enough to don the mask is another issue.....)

Maybe a chemist can speak about the gas laws and how they apply. Gas will expand to fill an available volume. At higher altitude there is less gas, therefor less pressure.

Got ya..! Crystal clear. Thanx.

[bcm119]

I think the composition of the atmosphere is constant up to about 100,000m. After that the lighter gases become more abundant than o2 and nitrogen.

The reason people get altitude sickness is that the air density drops as you gain altitude, so there is less oxygen per unit volume (eg., your lung!). "Less oxygen" can be misleading I guess, because there is not less oxygen in relation to the other gases, theres just proportionately less of all the gases per volume. 1 liter of air at sea level has less oxygen (and other gases) than 1 liter of air at 10,000ft.

[Tom]

Gravity sucks the molecules to the earth. So the gases are denser down here. Up there, you have to breathe harder to move more gases to get enough oxygen. Your brain swells up. Mild swelling you just get a little sick. A lot of swelling and you go cuckoo and then die. Or your blood vessels in the lungs start closing up, shunting all the blood through the ones that aren't constricted. Why? Cause it's fun to have a fluid leak into your lungs. You get all grey and start rattling. And then you die. If none of this happens to you, a rock breaks free up above and whacks you right on the noggin. And then you die. Or, you fall into a hole in the glacier. And then you die. Or a yeti takes a shine to you. And then you wish you died.

Boy, oh boy. Makes me want to go mountain climbing.

[saab2000]

Got ya..! Crystal clear. Thanx.

Clear as mud, I know, but I am not a chemist.... This is ultimately a chemistry question. Basically it is the pressure of the air at high altitudes is not enough to let your body absord the needed oxygen.

But bodies do adapt, hence altitude training, etc.

[saab2000]

Gravity sucks the molecules to the earth. So the gases are denser down here. Up there, you have to breathe harder to move more gases to get enough oxygen. Your brain swells up. Mild swelling you just get a little sick. A lot of swelling and you go cuckoo and then die. Or your blood vessels in the lungs start closing up, shunting all the blood through the ones that aren't constricted. Why? Cause it's fun to have a fluid leak into your lungs. You get all grey and start rattling. And then you die. If none of this happens to you, a rock breaks free up above and whacks you right on the noggin. And then you die. Or, you fall into a hole in the glacier. And then you die. Or a yeti takes a shine to you. And then you wish you died.

Boy, oh boy. Makes me want to go mountain climbing.

I just read an article about people who climb Mt. Everest. Some of the more diehard ones have actually done it without oxygen tanks. Unbelievable. Doing it at all is incredible. Doing it without supplemental oxy is even more so.

[Bradford]

where they speak English together.


I believe they all use babble fish.

[ada@prorider.or]

. 1 liter of air at sea level has less oxygen (and other gases) than 1 liter of air at 10,000ft.

well i doubt that

1 liter stays the same at least that what i learned at school

only to get 1 liter is a mater of pressure

1 liter of air stays the same
only if there is nothing to get 1 liter see in space

impossible to get 1 liter of air becuase there is none
so basicly it stays the same ,for me its more to get enough pressure to gain 1 liter

i compare it with 1 bottle of argon welding gas
you can put another gas with it with out increase the volume or the pressure
mater of gaps between the molecule´s

stays my other question about the viscosity
who can tell me the differance and why that is
1.20 density air 20 % humidity 20 degrees
1.20 desiity air 80 % humidity 20 degrees

is there any differance and so why?

[obtuse]

well i doubt that

1 liter stays the same at least that what i learned at school

only to get 1 liter is a mater of pressure

1 liter of air stays the same
only if there is nothing to get 1 liter see in space

impossible to get 1 liter of air becuase there is none
so basicly it stays the same ,for me its more to get enough pressure to gain 1 liter

i compare it with 1 bottle of argon welding gas
you can put another gas with it with out increase the volume or the pressure
mater of gaps between the molecule´s

stays my other question about the viscosity
who can tell me the differance and why that is
1.20 density air 20 % humidity 20 degrees
1.20 desiity air 80 % humidity 20 degrees

is there any differance and so why?


because humidity is the amount of water vapor in the air. given the air's denisty it can hold a certain amount of water vapor.
the warmer air is, the more water vapor it can "hold." dew point is the actual measure of how much water vapor is actually in the air. relative humidity is a measure of the amount of water in the air compared with the amount of water the air can hold at the temperature it happens to be when you measure it.

air density does not change based on humidity, dew point or relative humidity.

at least that's what my low level of education told me.

obtuse


cees-
you should consult some ballistics studies that deal with this stuff. i'm being a little simple minded about air density not changing based on humidity.

see here:
the effect of humidity is generally worst at locations near sea level on very hot days, but even under these conditions, the effect is small. for example, for a location near sea level on a 90°F day with barometric pressure the same for both situations, absolutely dry air (zero relative humidity) is not quite 0.02 percent MORE dense than air saturated with water vapor (fog, meaning 100 percent relative humidity). this seems strange; wet air feels “heavier” than dry air. But it is true because a water molecule weighs less than a nitrogen molecule, which it displaces if the pressure and temperature remain the same. this tiny change in air density is not completely negligible for long-range shooting (obtuse: but probably is for bicycles and other things travelling much slower than the speed of sound.) For example, under these same atmospheric conditions, the drop at 1000 yards for Sierra’s .308” diameter 168 grain MatchKing bullet fired at 2700 fps muzzle velocity will be about 2.4 inches more for absolutely dry air than for saturated wet air.

[ada@prorider.or]

Cees - What brought about your question?:D

i have a new software program for aerodynamics
and i had a discussion with specialist at aerospace center
this to simulate a specific problem
where we talked about pressure static pressure dynamic pressure kinectic energy
and humidity and the tag that it might cause
then i had to do a calc of gasses and was also having a discussion with firm to deliver me a oxygen measurement device (the guy was also a pilot ,a judge and cyclist) so we talked aerodynamics and gasses ,presssure
and.....yes humidity


i have to do a test tomorrow with my selve and oxygen machine ,i do this to determine in field on track and windtunnel the optimum meatabole position on the bike

well long story but it a part of work where i am working on now for olympics

[davids]

1 liter = 1 liter. That's weight.

Air is air. No one is shoving another gas into the mix for certain locales.

As pressure increases, the volume of one liter decreases. One liter fits in a smaller volume at sea level than it does at the top of Mt. Everest.

Another way of looking at this is that one cubic meter of air is denser at sea level than at the top of Mt. Everest. A cubic meter of air at sea level weighs more than a cubic meter of air at the top of Mt. Everest.

A lung-full of air at sea level weighs more than a lung-full of air at the top of Mt. Everest. That's because it is more dense. There's more oxygen for a given volume at sea level than at the top of Mt. Everest.

:confused:

[ada@prorider.or]

1 liter = 1 liter. That's weight.
:

well liter is volume not weight!

[OilyFish]

If this is serious:
Relative composition (O2: Ni: Co2 etc) probably remains fairly consistent from 0m to space. The relative density (of the entire composition) accros the height range will vary. So I would imagine that viscosity and available O2 per ltr will fall in a squared relationship according to height.
Whatever, I was puffing in the high Andes but I don't at home at sea level.

[Jeremy]

http://www.warwickmills.com/Inflatable-Fabric.html

In 1935 the Explorer II was launched, reaching the lofty height of 72,395 feet. In the link above, notice the carrot like shape of the balloon at take-off. It was inflated to less than 10% of its capacity. As elevation increased the volume of the gas would expand to full capacity. Same weight of gas, much bigger volume at altitude.

Jeremy

[zank]

PV=nRT
P = pressure
V = volume
n = # of moles of molecules
R = constant
T = temperature

This equation can help you, Cees. As you go higher in elevation, pressure decreases. Now, assuming the right side of the equation (nRT) is constant, then volume must increase. So, you can look at it two ways. 1 mole of air occupies more volume at higher elevations (lower pressure). Or, 1 liter of air contains fewer moles (molecules) of air at higher elevations (lower pressure). In both cases the air is less dense.

Dry air is more dense than humid air. This is because water vapor displaces O2 and N2 (which are heavier molecules than H2O) as humidity goes up.

http://www.engineeringtoolbox.com/molecular-mass-air-d_679.html
http://www.engineeringtoolbox.com/density-air-d_680.html

I hope this helps. I am not a chemist, but I am a chemical engineer.

[slowgoing]

I am not elegant on speaking/writing of these matters, but I know in my own head what I am talking about.

Post of the day.

[davids]

well liter is volume not weight!
Exactly. Take the same gas. Pressurize one 1 cubic meter sample to equal sea level. Pressurize a second 1 cubic meter sample to equal 10,000 meter altitude. The more highly-pressurized 1 cubic meter volume will have more gas in it than the less-highly pressurized 1 cubic meter volume - It will weigh more.

It will weigh more because there is more material in that volume. More air per cubic meter. More oxygen per cubic meter. More oxygen per lung-full.

[Jeremy]

http://www.sd4history.com/Unit9/stratobowl.htm

This is a photo of Explorer I shortly after take-off. It contained 225,000 cubic feet of hydrogen gas and was expected to expand to 3,000,000 cubic feet at very high altitude.

Jeremy

[saab2000]

Post of the day.

Thank you. Thank you. The crowd goes wild.

I had a heckuva trip the last few days and am delirious from exhaustion. Hopefully tomorrow I will be more coherent and eloquent.

[ada@prorider.or]

http://www.engineeringtoolbox.com/molecular-mass-air-d_679.html
http://www.engineeringtoolbox.com/density-air-d_680.html

I hope this helps. I am not a chemist, but I am a chemical engineer.

i looked at this
but cannot find any formula of change in viscosity of air
with humidity
i do not know or it change´s

[Skrawny]

The volume never changes.
1 liter = 1 liter

The percentages of gasses essentially never change.
ie: "air" is about 21% oxygen molecules, and about 70% nitrogen molecules

The TOTAL NUMBER OF MOLECULES per liter drops as you go up in altitude. The ratio (see above) remains the same.

Your lungs move VOLUME, not number of molecules nor percentage of molecules. If the air is half as dense, you have to breathe twice as much to get the same number of oxygen molecules.

To belaber the point further:
lets say I had a tiny balloon that fit 100 molecules, and I filled it with air at sea level. 21 of the molecules would be oxygen, 70 of them would be nitrogen and 9 would be other stuff. If I took it to the top of a mountain, the balloon may get 3 times as big, but it still would contain the same number of molecules, if I took it under water, it may get on third the size, but the content still would not change!

[bcm119]

well i doubt that


1 liter is a measure of volume, so 1 liter of air at sea level will have a greater mass than the same volume of air at 10,000 ft. If you raise the pressure of the air at 10,000 ft it would fit into the 1 liter volume... I don't understand what you're getting at.


who can tell me the differance and why that is
1.20 density air 20 % humidity 20 degrees
1.20 desiity air 80 % humidity 20 degrees

is there any differance and so why?

Air of the same temperature but with different water contents will have different densities. Moist air is less dense than dry air at the same temp. In other words, if you have 2 air masses, both with the same temp, the air with the lower dewpoint will be denser. Thats basic meteorology, but I don't know enough chemistry to explain why that is...

[catulle]

the effect of humidity is generally worst at locations near sea level on very hot days, but even under these conditions, the effect is small. for example, for a location near sea level on a 90°F day with barometric pressure the same for both situations, absolutely dry air (zero relative humidity) is not quite 0.02 percent MORE dense than air saturated with water vapor (fog, meaning 100 percent relative humidity). this seems strange; wet air feels “heavier” than dry air. But it is true because a water molecule weighs less than a nitrogen molecule, which it displaces if the pressure and temperature remain the same. this tiny change in air density is not completely negligible for long-range shooting (obtuse: but probably is for bicycles and other things travelling much slower than the speed of sound.) For example, under these same atmospheric conditions, the drop at 1000 yards for Sierra’s .308” diameter 168 grain MatchKing bullet fired at 2700 fps muzzle velocity will be about 2.4 inches more for absolutely dry air than for saturated wet air.

That's amazing. No wonder the Polish snipers in Irak have a rate of 80% scores at 600 yards. I like this dialogue between Dense and Obtuse.

[davids]

Is it a language barrier? This doesn't seem like a difficult concept to me.

Good luck, Cees.

[ada@prorider.or]

[QUOTE=bcm119
Air of the same temperature but with different water contents will have different densities. Moist air is less dense than dry air at the same temp. ...[/QUOTE]

i know this
but my feeling is same temp air density but differant humidity change the viscosity of air

thus also the drag (at least that my feeling)
but cannot prove this with a formula

if this is so you can influence the boundary layer of a object

[catulle]

Jeeezzzz, don't y'all know that a kilo of lead is heavier than a kilo of air?

[ada@prorider.or]

Is it a language barrier? This doesn't seem like a difficult concept to me.

Good luck, Cees.

its not difficult but see this way to simulate high altitude
you just reduce the pressure

as for training reduce the presure only of the air that you intake leave evrything else the same

[zank]

i looked at this
but cannot find any formula of change in viscosity of air
with humidity
i do not know or it change´s

Kinematic Viscosity is inversely proportional to density. So, as the humidity increases, the density decreases and Kinematic Viscosity increases.

So, it seems that humid air has a higher kinematic viscosity than dry air.

http://www.engineeringtoolbox.com/dynamic-absolute-kinematic-viscosity-d_412.html

[ada@prorider.or]

the density decreases and Kinematic Viscosity increases.

[/url]

again the density stays the same in my question
and that kinematic viscosity increase that is locig
hence there is less force to avoid the air or liquid to flow
so its flows better and thus increase´s


but that not the question

[zank]

Ah, there is the flaw. If you have 2 samples, one at 90% humidity and 20 degrees C and another at 20% humidity and 20 degrees C, we have shown that they will not have the same denisty at 0 meters. They can not both be 1.20 at 0 meters.

[stevep]

is this air?
or hot air?

[catulle]

is this air?
or hot air?


It's a kilo of air, dude. Get it...?

[ada@prorider.or]

Ah, there is the flaw. If you have 2 samples, one at 90% humidity and 20 degrees C and another at 20% humidity and 20 degrees C, we have shown that they will not have the same denisty at 0 meters. They can not both be 1.20 at 0 meters.

no that not true
the density can stay the same
only the local pressure change´s

the both case´s the density is the same!!!!!

remember density is something else then pressure

[Skrawny]

I think Zank's got it.
Add more water to the same volume of air, you get a higher density.

[ada@prorider.or]

air 20 celcuis
pressure 1013
humidity 20%
air density 1.200



air 20 celcuis
pressure 1019
humidity 80%
air density 1.200

[zank]

no that not true
the density can stay the same
only the local pressure change´s

the both case´s the density is the same!!!!!

remember density is something else then pressure

OK, to go any further, please set your assumptions. You have...
Temperature
Pressure
Volume
Humidity
Elevation
Air Density
Air Kinematic Viscosity

What variables are fixed and what are you changing? And what is the question you are asking?

Your original question was
"by why do people say on altitude let say 5000 meters there is less oxygen wich is not

only the pressure is differant

but why people say that?"

Others have answered this. There are fewer molcules of O2 per liter of air at higher elevations than lower elevations because the air is less dense at lower pressures.

Your second question was
"if you take air on zero meters
with density of 1.20 with 20 % humidity 20 degree C
en
density of 1.20 with 90 humidity 20 degree C

wich has a better viscosity?
and
why"

If the density of the air is fixed at 1.2, it does not matter what the composition of the air is because Kinematic Viscosity is a function of air density, not humidity.

[bcm119]

I think Zank's got it.
Add more water to the same volume of air, you get a higher density.
Actually its the other way around, which Zank pointed out earlier... strangely enough. Water vapor molecules are less dense than the other gases they replace.

[ada@prorider.or]

If the density of the air is fixed at 1.2, it does not matter what the composition of the air is because Kinematic Viscosity is a function of air density, not humidity.


that is the kinematic viscosity
i have it about moving through the air
so the viscosity it selve
so dynamic or absolute viscosity
The absolute viscosity can be expressed as

μ = 1.113 × 16.97 10-6

= 1.88 10-5 kg/ms (Ns/m2) (P)

if you take this formula then you would say the dryer the air(=less pressure 1013 with the same density) the lower the viscosity
so more drag becuase the viscosity is lower then


with a higher pressure(1019) with more humidity

?????

am i right?

[rwsaunders]

PV=NrT.

[OilyFish]

Ask the experts:
http://www.grc.nasa.gov/WWW/K-12/airplane/airprop.html

[Jason E]

Ok, at this point I'm not sure what is not being gotten here.

Cee's, you are in an empty room. You lay on the floor. Jan Ullrich walks in with a bucket of M&M's chocolate candy. Problem is, the old Jan doesn't know when to quit, so he keeps bringing in the M&M's until the room is full. Really full to the ceiling.

Pevenge likes to check his progress as this is all training for the Tour, so he inserts scale every time Jan puts in another foot of M&M's while Tobias carefully measures every single M&M to make sure they are all identical in size and weight.

One of the scales are on your chest, and others are stacked up in the layers of M&M's up to the beautiful 14 foot ceilings in this room somewhere in South Africa. The scales transmit their data from the different depths of chocolate heaven through similar technology to that of the wireless SRM, which have yet to be proven to work well in chocolate.

Now Every M&M weighs the same, hardly anything, but you are crushed. The scales near the top only measured a few pounds of pressure though.

Their is less pressure near the top, and less pressure on the M&M's near the top. Jan reaches down from a balcony above to easily grab some and sprinkle them on Ice Cream, yet the ones on the bottom have the weight of all of those above them, making it near impossible for you to move at all.

Now, increase the scale, and call it air. Composition remains the same, while the amount found in a given theoretical invisible box of any given size is far less at the top.

http://www.meloncorp.com/sw/31/pelucheg.jpg

[OilyFish]

Exactly, everyone competes at the same altitude in a given comp. They may take the same M&Ms. (USPS / DISCO excepted.)

[obtuse]

that is the kinematic viscosity
i have it about moving through the air
so the viscosity it selve
so dynamic or absolute viscosity
The absolute viscosity can be expressed as

μ = 1.113 × 16.97 10-6

= 1.88 10-5 kg/ms (Ns/m2) (P)

if you take this formula then you would say the dryer the air(=less pressure 1013 with the same density) the lower the viscosity
so more drag becuase the viscosity is lower then


with a higher pressure(1019) with more humidity

?????

am i right?

cees-
given what i posted before; probably not enough of a difference to warrant a control for.

you are obviously concerned with the affects of humidity and altitude in regards to drag and aerodynamics. consult ballistics people and aeronautical engineers for this. they have done the most work on this subject. obviously the speeds are different and the sizes of the objects in question are different but atmospheric stuff stays the same.

obtuse

[catulle]

cees-
given what i posted before; probably not enough of a difference to warrant a control for. :no:
obtuse
.