An ongoing argument that i can't seem to settle. Say two identical cars with the same total weight are traveling at each other at 100km/h and hit head on. Would this be the same as one vehicle hitting a brick wall at 100km/h or would the speeds combine and come to 200km/h? Assume that the brick wall will "give" or crush to the same degree as the crumple zone of the cars (or simpler, assume in the second example one vehicle strikes another one that is backed up against an immovable brick wall). Thanks for your input!