🚀 go-pugleaf

In article <1992Nov5.130316.28438@kth.se> e92_anh@vaxkab.lne.kth.se writes:
>This will probably sound like a silly question to a lot of you, but WHY
>does a helium-filled balloon rise upward? Is it because of the
>difference in air-pressure at the balloon's top and bottom, causing the
>resulting force to press it upward?

Yes, that is correct. It is most easily seen to be quantiatively correct for
the case of a vertically oriented cylindrical baloon, a hard kind to find at
your average toy store!

>Thus, consider this: If the air surrounding the balloon had exactly the
>same density on all sides, then the balloon would not move (I think).

Well, that is correct, but it's a second order effect, and not causal in this
case. The pressure's the thing, and of course density is inversely proportional
to pressure.

>So, is my airpressure-theory correct? I'd very much like to know!

Yes it is, you'll be glad to hear! :-))

Leigh