How do you calculate the speed at which one objects hits another. I know the initial speed , the deceleration and the distance. Is there anything else I need to know. The car was travelling at 110km/h it decelerates at 6.5 m/s and hits a wall 25m away . so what formula do I use to calculate the speed at which the car hits the wall? Could I in any way also calculate the amount of time it took until the car hit the wall?