Interesting question...

So, there you are, flying along in your Cessna 172SP when you notice a fly with a weight of "x" ounces sitting on the instrument panel.

You swish at the fly and it starts buzzing around the cockpit.

Does the fly, while flying in your flyer, impart any weight to the aircraft?

His weight is being supported by the flapping of his wings.

If lands again, then the plane is supporting his weight.

in the mass of air enclosed in the aircraft.

...I see the conundrum. I almost responded in that way, but changed my mind.

Crap. Now my brain hurts. This is why I'm not an engineer.

where does the force from it's wing flaps go?

I could be wrong...

It's just physics, dude. Though I did almost choose the purple monkey option... I like that one.

It would have a certain mass when the fly was at rest. But when he/she was in flight, it would be supporting itself by flapping its wings. But it would also be exerting very slight, but theoretically measureable, air pressure forces on the inside of the cockpit. These forces, in reality probably would cause the framing of the inside of the cockpit to move slightly. This in turn would raise the temperature to rise slightly, much like a piece of plastic does when you bend it in a fast fashion for an extended period. But in much smaller amounts.

But, I ramble. Getting back to the point - I theorize that it won't weigh as much, but it's sum of kinetic and potential energy is a constant.

I could be wrong. It's been a while since I had physics...

but I do love this forum. :)

The fly's wings exert a downward pressure on the air. The air ultimately presses against the airplane, so his weight is still added.

Another view - you put a large fan inside the airplane. Place a mass above the fan. Of course it adds to the weight. Now you flip the fan on and support the weight. Does the weight of the airplane decrease? No!

You really should share.

jk

That means I don't know the answer.

relative to an external observer, yes, he is giving his weight to the aircraft... relaitve to you inside the cockpit, no.

everything is relative to something else, its the only way we can note anything like speed, velocity, orientation, mass, weight, temperature, ect.

-LK