Final answer:
Seat belts and safety features like airbags prevent severe injuries by applying the concept of impulse, which distributes the impact force over a longer period. This reduces the forces felt by passengers, and such safety designs are crucial for minimizing harm in accidents.
Step-by-step explanation:
The purpose of seat belts and shoulder straps is to protect the occupants of a vehicle during a crash by restraining them in their seats. This prevents injuries from contact with the interior of the car, such as the steering wheel, windshield, and dashboard. The physics principle behind this is the concept of impulse, which is the product of the net force acting on an object and the time duration of that force. Ensuring that the force involved in stopping the person acts over a longer time reduces the severity of the force, thereby minimizing injury.
Governments enforce seat belt laws to reduce medical and caregiving costs arising from accidents. Additional safety features in cars include airbags and padded dashboards, which also work on the impulse principle to reduce impact forces. The design of modern cars with components that can crumple in a collision extends the time of impact, further reducing the force exerted on passengers and lessening injuries. This has been seen in the dramatic decrease of fatalities in car racing due to the introduction of crumpling car frames.
For example, consider a car accident where a car moving at 10 m/s crashes into a tree and stops in 0.26 s. If a passenger inside the car has a mass of 70 kg, the seat belt must exert a force on them to bring them to a halt safely. By calculating the impulse, we can determine the seat belt's force, significantly less than the force experienced without a seat belt, thus illustrating the importance of such safety features.