Relativity

[emmaareitch]

If fly gets into your car thru an open window while it is stationary and doesn't land, what will happen to it if the car moves if it has not landed anywhere on the inside? Will it bang against the rear somewhere as soon as the car reaches a certain speed if it just continues to hover?

[rekstout]

Ignoring air currents etc.

Mostly hover because the air it is flying in is being moved as well and the fly is hovering relative to the air it is in. However, because air is a very thin medium, the fly's hovering position would probably move toward the back of the car as the fluid air is shunted toward the back of the car, this would be more apparent in rapid acceleration. If the fly were hovering in a vacuum then it would indeed just hit the back window.

[xyzzyplugh]

To help answer, imagine standing in the corridor of a speeding train and you jump, do you land in the same spot? Now, still in your imagination, try the same jump on a speeding open back truck. A relativitily merry christmas to you emmareitch

[smorodina]

It will bang against the rear, because of the acceleration of the vehicle. Anything loose in the car will tend to do the same, like the things on the shelf at the front which fall off if you accelerate fast enough. The same if you brake hard.