Final answer:
Headrests prevent neck injuries by minimizing the backward motion of the head in rear-end collisions, reducing the risk of whiplash.
Step-by-step explanation:
Headrests should be adjusted so that the head restraint contacts the back of the head. This prevents neck injuries if you are hit from behind. The anterior longitudinal ligament in the neck is important for resisting excessive backward bending of the vertebral column. In rear-end collisions, if the head is not supported, it can whip back, stretching or tearing this ligament, leading to whiplash injuries.
Properly adjusted headrests help to minimize the motion of the head relative to the body, thus reducing the chance of whiplash. Car safety features, like airbags and seat belts, function similarly by extending the time over which the forces during an accident act on the body, thereby reducing peak force and risk of injury.
Crumple zones in cars reduce the force on passengers by extending the impact time. Together with headrests, they form an integral part of automobile safety systems, significantly decreasing the likelihood of injuries in various types of collisions.