From: utzoo!decvax!cca!hplabs!hao!menlo70!sytek!zehntel!teklabs!ucbcad!ARPAVAX:CSVAX:npois!houxi!ihps3!ihuxv!lew@sri-unix
Newsgroups: net.physics
Title: balloon explanation
Article-I.D.: ihuxv.232
Posted: Mon Aug 16 08:32:45 1982
Received: Fri Aug 20 02:48:31 1982

Having received two requests for explanation of the Helium-balloon-
in-the-accelerating-car effect, I'm posting this.

The air in the car sloshes to the back, pushing the balloon to the front.
It behaves like a bubble in a sealed bottle of water.

More abstractly, in the car frame of reference, the fictitious force
which pushes you into your seat adds to the force of gravity (vectorially),
creating a force field slanting down and to the back. A Helium balloon,
being buoyant, anti-aligns with this force field (assuming it is tethered.)

				Lew Mammel, Jr. - BTL Indian Hill