all things being equal, the speed of the first ball is equal to that of the last. the weight of the two cars, plus the friction between the tires and the road surface factor into the analysis. >> the coefficient of friction is basically just a measure of how slippery that surface is. so that's a very important piece. the other thing is the angles that are involved with approach and departure from the impact area for vehicles that are involved in a collision like this. >> scotland used surveying equipment to measure the distance the parked car moved after impact as well as the angles of impact. a computer program performed the physics calculations, and the result, steve's jeep was traveling between 38 and 42 miles per hour when it hit the parked car, not 60 miles per hour as he claimed.