Final answer:
Air bags enhance frontal protection during collisions but are not as effective in side or rollover accidents, thus emphasizing the importance of always using lap and shoulder belts. The principle of impulse explains how airbags reduce injury by extending the time over which collision forces act, thereby distributing the forces more gently.
Step-by-step explanation:
Air bags provide supplemental protection to the frontal body region. They offer little protection in a side or rollover accident. For maximum safety, lap and shoulder belts should always be used. Understanding the concept of impulse, which is the product of the net force and the time over which it acts, can explain how airbags improve vehicle safety. In the event of a collision, the same momentum change occurs regardless of airbag deployment, but the force on occupants is much less because it acts over a longer time, thanks to the cushioning effect of the airbag. Additionally, modern cars with plastic components and designed to crumple upon impact also increase collision time, leading to reduced force and improved safety. These design features, including airbags, have significantly decreased fatalities in vehicle collisions since they allow the vehicle and its safety features to absorb the brunt of the collision force, better protecting the occupants.