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G0FUM > INFO 18.07.02 13:32l 88 Lines 2646 Bytes #999 (0) @ WW
BID : B97389G0FUM
Read: DB0FHN GUEST
Subj: Re: Balloons/Hot Air
Path: DB0FHN<DB0ZWI<DB0CHZ<OK0PKL<OK0PPL<RZ6HXA<IK1ZNW<ON0BEL<ON0AR<GB7FCR<
GB7IPW
Sent: 020718/0904Z @:GB7IPW.#38.GBR.EU #:15663 [Worthing] FBB $:B97389G0FUM
From: G0FUM@GB7IPW.#38.GBR.EU
To : INFO@WW
Hi All,
The easiest way to assimulate Balloons rising etc is down to
pressure basicaly.
Atmospheric pressure reduces the higher you go due to the gravitational
pull of the earth on the air surrounding our planet.Air has density
therfore weight/mass.
Hot air is more rarified than cold air so is lighter, as the molecules
are more widely spaced (Less dense). therefor the average atmospheric
pressure is greater than the hot air, so it will rise to find an equal
pressure.
Helium is lighter than our atmosphere air so if enclosed in an envelope
the atmospheric pressure tends to squeez it and it rises untill an
equalibrium of pressure is reached or another way the Helium and
atmospheric gasses eaqualise in weight and pressure.
An example of the above is, the moon has no atmosphere therefore no
atmospheric pressure. A balloon filled with Helium would fall like a stone
on the moon's surface as the Helium and surrounding envelope would have
nothing to support it.
Now moving on to another aspect. If you blow up a balloon then let the
spout go the escaping air will propel the baloon like a jet engine.
Now what is it that does the propelling,
Is it the jet of air ejecting from the balloon? NO
It is the pressure inside the balloon that creates the motive force.
A sealed balloon has an equal pressure on all its inside surface. If one
point on that surface is opened then the pressure on that side is reduced
.
The unequal pressure on the inside of the balloon will cause the side with
the higher pressure to move away from the side with the lower pressure.
This is how a Jet Engine works.
A rocket works by the same principal.
Or firing a bullet in a gun,The Gun tries to go in the opposite direction
to the bullet, the greatest pressure being between the breach and the
bullet.The bullet in effect tries to stand still and the gun tries to move
away from it.
All with the same principal.
Thats my tuppence worth.
Cheers
73 - Alan, G0FUM @ GB7IPW
Worthing West Sussex
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73 - Alan, G0FUM @ GB7IPW
Worthing West Sussex
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