Mark Hickey wrote:

Richard Lamb wrote:


Air is sure strange stuff...


One of my favorite physics lesson is what happens when you have a
helium baloon floating in the back of your car.

Hit the gas, it flies forward.

Stomp the brakes, it flies to the back.

Or more accurately, the air in the car does the opposite.

Mark "light is relative" Hickey

Neat!

I've been thinking about that pervious odd behavior of the blimp.

Try this on for size?

The air coming out of the vent hits the floor and spreads out.

Being warmer than the air around it, it starts to rise.

The stream blowing from the vent causes a lower pressure area
around it, causing the air rising from the floor to move back
in toward the stream.

That's a basic convection circulation system.
So the dumb blimp wanders over toward the down flow coming from above.

The lower pressure around the stream is what caused the blimp to stick
to the down flow. (it never did go completely into the stream.
Just stuck to the side of it.)

Now the air in the flow is warmer than the air in the room, and the
blimp's helium temperature is still at the lower room temp.

But the He warms quickly, expanding the bag a bit, and causing the
blimp to defy not only gravity - but the direction of the stream,
and rise up to the very attractive vent.

THEN, as the temperature in the room increased, and matched the temperature
of the blimp, the silly sated think sank back to the floor.


Anybody buy into that?
Or is this as demented as that TRUTH guy???

Richard