If a vehicle hit any other object then its speed will slow down or some time the vehicle will stop its depends on the force exerted by other object on the vehicle.
The change in speed of vehicle is due to momentum because momentum is always conserved. So to conserve the momentum the speed of the vehicle decreases because after hitting the overall mass is increases.
Homeostasis is the tendency toward a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes.
