Along the freeway, you may occasionally see barrels filled with water placed in front of a bridge abutment, or other obstacle, as a safety measure. The driver of a car that hits the barrels is much more likely to survive than the driver of a car that hits the obstacle directly. The car has an initial momentum, due to its initial velocity and its mass. When the car has come to a rest, its final momentum is zero. Since the momentum changes, there must be an impulse acting on the car.
Impulse is average force multiplied by the time that force acts.
The water filled barrels bring the car to a stop over a longer time interval. This requires a smaller force to create the impulse necessary to stop the car. If the car hits the bridge support directly, it is brought to a rest in a much shorter time interval, meaning a larger force is necessary. Large forces will tend to injure the occupants more.