Originally Posted by MarshyTheKid
You lose... If the car is accelerating and the belt has a sensor to speed up at the same rate as the car, matching speed for speed no matter what, the car won't go anywhere.
Ok...so we can have a car that's moving at 10mph relative to the ground on a conveyor that's moving -10mph relative to the ground, thus satisfying the riddle. The car will be going 20mph relative to the conveyor...but that is irrelevant.
If you don't get it, go to an airport and run against one of those moving walkways. Let's say it's moving at 3mph. I can bet you any amount of money that I can run on that conveyor (in the opposite direction) such that if you shoot a radar gun at me it will say 3mph. I might have to move my legs twice as fast, but that's beside the point.