[JkWhoSaysNi]

The difficult part is detecting where it hits the car and calculating how the car should react (e.g. bounce off or come to a complete stop or just slow down but continue moving or whatever) depending on the angle it hits and the speed it's travelling.

Unless the car is small, using the X/Y co-ordinates will not work because probably that part of the car is not on the wall.

You need to detect ahead of the direction the car is moving and for the width of the car, or do multiple checks.