if you're travelling in a bus which is doing 35mph and you jump up in the air, you don't hurtle backwards down the bus at 35mph, so i guess the fly maintains its position in the bus.
Ahhh, but you dont fly backwards because you are already in contact with the bus when its moving..
The fly question can also bring up... if you leap into the air the instant before the bus sets off, will you land further back than you began?
i think someone is going to have to try it out
I recon the answer is different for the person than for the fly.
The fly will move with the bus because it has very little inertia so, as the air in the bus moves forward, it will push the fly with it.
If a person jumps just as the bus sets off, the person will land further back in the bus because he/she has a large momentum keeping him/her stationary.