Not everyone has.

You're welcome.

 

[QUOTE=03_AP1,Dec 6 2005, 05:28 PM]
Here's my shot in the dark, but I think the balloon will too, because in a moving car, the air inside the car is also moving at 45mph - assuming the car is sealed.

 

so what does the bouyency have to do with it?

If I had a tennis ball in my hand, and tossed it straight up just as I hit the wall, it would momentarily be bouyant would it not? And it would shoot forward on impact.

 

The plane will NOT take off. There are two scenarios that prove this.

Scenario one: Design and construction of the enormous conveyor are awarded to the low bidder on a fixed price basis. This leads to the contractor cutting corners and catastrophic failure of the belt mechanism during testing destroys the aircraft before takeoff. Plane never leaves the ground (unless, of course, it is accidentally catapulted onto the nearby highway using the slingshot effect, but this is explained more by conservation of stupidity than actual "lift").

Scenario two: Design and construction of the conveyor are awarded to the low bidder on a cost-plus basis. Price overruns and an unfortunate change in government administration cause the project to be cancelled before the belt material is selected. Again, the plane stays planted to the Earth.

There is a third scenario which involves Haliburton, but I'll leave that for the politics forum.

 

A tennis ball is more dense than air, therefore it is not buoyant in air. It may be momentarily hanging in the air, but it is not buoyant. A helium balloon is buoyant in air, so it is going to act differently. Hint number 2: Ignore gravity, think density.

 

I performed this experiment for my children when they were young and later with my grandchildren.

Instead of a VCR, I use a couple of balloons filled with air, and a couple with helium. I never get tired of seeing the results.

 

Ok, here's my semi-educated guess: the VCR will obviously move forward, perhaps crushing your skull in the process, but the helium-filled balloon will actually move towards the rear of the car (in the car's frame of reference). As the car decelerates, air pressure at the front of the car increases. Helium weighs less than air, being less dense, and the increased pressure at the front of the vehicle will actually push the less dense balloon backwards. The same effect can be observed when driving with Britney Spears.

 

I'm gonna join VoIPA on the limb on this one. The buoyancy (and drag?) of the balloon trying to move through the air will make it decelerate faster than the air that surrounds it, so the balloon moves backwards in the car.

at your previous post, btw, V .

 

Sorry, T. I was editing my post as you were typing yours. I decided to expand on my reasoning a bit...

 

Can you tell I'm a former Civil Servant?