Relative Velocity with Flies

I've been reading a little physics on the side. . . . You have probably come upon the classic problem of whether a fly, inside a car going 80 kph and flying from the back to the front of a car itself, is going 80 kph or faster. I've been having so much fun with this one.

Consider:

— fly's velocity relative to car vs. total velocity relative to Earth

— fact: max velocity of fly itself, flying in still air but not a vacuum, is approximately 80 kph

— if a vacuum existed inside the car, the fly would never have the guts to do that again (but then it wouldn't have been able to lift-off anyway)


So the most interesting thought I had about it was that the potential total velocity of the fly in the car would be 160 kph. Wow. Over-achiever, the fly that does that!

Aside:  I once read that in many single car accidents, a large dead insect is found in the car. Theory has it that the driver loses control while swatting at it. Get a grip on yourself and don't do this.