• Blv

MemberDec 21, 2013

## Why does lower density air move upwards?

As density of the air decreases it starts flow upwards its quiet commonly know to all of us? But what is the reason behind that,how it move upwards?
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Replies
• MemberDec 24, 2013

dear, this happens because of density difference.
as we know that air is more denser at bottom(near surface of earth) as compared to the atmosphere at upper level or we can also say that the density of air decreases as we move up.

Now consider that there is air all around you, now anyhow you can able to make some part of air less denser as compared to remaining air around you. As the air becomes less denser it tends to move up because of density difference from high denser air to less denser air. that's it....

i hope its clear to you, if any doubt fell free to ask....
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• MemberDec 24, 2013

I'm asking how it move upwards like apple falls on newton he find that due to gravitational force it falling towards earth. my que is how it lower density air move towards space (opposite to gravity)
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• MemberDec 24, 2013

Less density means means less weight.
Take a glass put water then pour honey.
Same happens with gas also.
What is lighter, comes at surface.
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• MemberDec 25, 2013

Blvn Lakshman
I'm asking how it move upwards like apple falls on newton he find that due to gravitational force it falling towards earth. my que is how it lower density air move towards space (opposite to gravity)
dear this is what i am explaining you. like gravitational force, a force is generated by density difference which forces the air to move from high density to low density..... try to understand..... 😀
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• MemberDec 25, 2013

Another way to look at it - lower density air is not moving upwards; it is being displaced by higher density air, which is heavier and is moving downwards because of gravity.
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• MemberDec 27, 2013

simple density=mass/volume assuming volume to be constant(at the given temperature and pressure) so low density= low mass so lower weight and so it will float up as the heavier air will displace the lighter air
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• MemberJan 15, 2014

Anand Tamariya's answer is very explaining. The gravitation is downwards and denser air is replacing the less dense air's place.

The mechanics can be explained more throughly by a chemist or a physicist. It must be about the vibration speed and amplitude of air molecules but I don't have anymore information about it.
But I know that the mechanics is different than the mechanics between low density and high density materials (two different molecule types). I believe that one is about the volume and molecular weight of the molecule.
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• MemberMar 22, 2014

the reason is buoyancy force, say there is a packet of gas with volume 'V' having density d1, surrounded by gases having density d2. now we say (d1)<(d2).
now buoyancy force equals to the weight of fluid displaced, and it acts in the upward direction. => buoyancy force = (d2)*V*g
but the weight of the fluid having density (d1) = (d1)*V*g and this acts downwards
since (d1)<(d2), upward force is more than downward force,the gas moves up.
Now the most common reason for desity difference is the difference in temperture.

i hope it helps
all the best
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