the below laws apply to physics in the known universe, if you take an object out of the known universe, who knows what will happen to it. i think it is safe to say that the physics inside of a wormhole are quite different. when inside this "buffer zone" all memory of the object is lost because the wormhole is not really inside the universe, but outside the universe. when it re-enters the universe the object would have to start from point one, thats just my theory anyway. and i don't have any way to prove it, its really just an idea. wormholes probably don't even exist. we are not talking about space here, there are likely many forces on an object inside of a wormhole (such as friction) that would bring the car to a stop because it has no method of propulsion. so conservation of momentum and enegy don't apply. firstly: THE LAW OF CONSERVATION OF MOMENTUM. In a system with no net outside forces acting on it, momentum is conserved. Unless time travel somehow slows the car down by imparting a force to it, it must keep the same momentum before time travel as after time travel. This means it has the same "velocity" after time travel as it did before time travel. The velocity of an object is a property of it that it possesses at any one time. If you took an object from where it is and moved it instantly to another place (or time), all properties should stay the same, including velocity. This would especially apply to wormhole time travel, which I assume is used my the Doc's car. secondly: THE LAW OF CONSERVATION OF ENERGY. If the car enters the time travel vortex or whatever you want to believe, it has a certain kinetic energy. Quite a bit actually. This cannot simply disappear. It must be transfered to something else, which it doesn't seem to, or stay as it is.