Final answer:
A person not wearing a seat belt in a head-on collision moves forward due to inertia. Inertia is the resistance to change in motion, and safety features like seat belts and airbags work on the principle of impulse to reduce force by extending the time of impact.
Step-by-step explanation:
A person in a head-on collision, who is not wearing a seat belt, continues to move forward at the car's speed because of inertia. Inertia is the tendency of an object to resist any change in its motion, including a change in speed or direction. According to Newton's first law of motion, an object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
In the context of car accidents, understanding the concept of impulse is critical. Impulse is the product of the net force applied to an object and the time over which it acts, and it results in a change in momentum. Safety features such as seat belts and airbags increase the time over which the net force acts, thus decreasing the impact force and improving the chances of survival and reducing injuries in a collision.