Which weighs more a pound of feathers, or a pound of lead?
Har, Har.

Jetts

The weigh the same, but density is an entirely different matter.



About the airplanes and breathing, that explination is very good. In that case, wouldnt it mean that since the fly is fliing in the jar, the pressure under it would be greater than above. Therefore, the jar would be forced downward the amount that the fly weighs. I believe the explination shoe made just ended this discussion.

Reminds me of the guy in the truck who jumped out at each stoplight and pounded on the sides. When asked why by a curious pedestrian, he replied, "Some fool loaded two tons of canaries in this one-ton truck; I've gotta keep half the little buggers in the air at all times!"

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So what if its a fish bowl with fish and water instead of flies and air. I say it weighs the same as long as the air tight lid is on the jar. With no lid it would be like sinking the fish bowl under the water and having a fish swim inside. [:-]

Gentlemen,

This same brainteaser has often been mentioned to full-scale student and licensed pilots. Even though it is ultimately a physical laws question and answer, RC and full-scale pilots often appreciate the physics behind the answer as can be seen by the size of this thread. In the aviation example it goes like this:

Consider a 747 (but any aircraft will do) loaded to its maximum payload weight in birds. Later when the airplane is in cruise flight all the birds take to flight inside the aircraft at the same time. Will the aircraft now be lighter and suddenly accelerate and climb because all the birds are in the air in the cabin?

As many here have pointed out similarly, the answer is that the aircraft's weight is unchanged, such as the weight of the jar with the flies is, (and therefore the pilots will not have to wrestle an out of trim aircraft whenever any number of the birds decide to fly around in the cabin).


See my new post in the aerodynamics forum for a new twist on this, titled "another brain bender"