> > > This whole thing reminds me of the conundrum, if that's the word, of the bird in the cage. If a bird is in an airtight cage attached to a scale and it starts to fly, will the scale read the same or less than before? I believe the answer is no as the bird still exerts downward pressure on the air below which in turn affects the scales.
> > > Am I right in thinking this?
> > >
> > > Bea 'Materials science degree didn't really cover this' sty
> >
> > OK, I have NO IDEA on that one. Anyone else got something? (The principles seems sound... It's just very weird.)
> >
> > Don
>
> Well, I'll see if I can take a whack at this. Let's see. I predict that, as the bird jumps up from the bottom of the cage to begin flying, the scale will first read more, as the bird exerts a downward force to push off. Also, every time the bird flaps its wings down, the scale will read more then before. When the bird move its wings up, however, I believe that the scale will read the same as just the bird cage, as the bird does not exert a downward force, as it would be in freefall for that small amount of time.
>
> -Ka"Great. Now where am I to find a bird and a really big completely air-tight cage to work with?"z!

I'd guess that, in any airtight cage large enough for a bird to fly in, a scale would read it as being lighter when the bird is flying. The pressure created by the wings wouldn't be wholly transferred to the floor; some of the pressure would go outwards to the walls of the cage.

gab"But the bird would suffocate"by