Final answer:
Modern cars are made with parts designed to crumple or collapse upon impact, increasing the collision time which decreases the net force on passengers, thus reducing injury risks due to the concept of impulse in physics.
Step-by-step explanation:
Cars designed to crumple or collapse in the event of an accident help protect the passengers by extending the time of impact. This longer time of impact decreases the net force experienced by the occupants during a collision. The principle behind this is known as the concept of impulse, which is the product of the net force and the time over which this force acts. The aim is to increase the collision time so that the same change in momentum occurs over a longer period, resulting in a smaller net force and thereby reducing the likelihood of injury.
Physicists explain this by the equation Δp = Fnet Δt, where Δp is the change in momentum. When Δt (collision time) increases while Δp remains the same, Fnet must decrease. This is essential in an automobile accident because it's the force during impact that can cause serious harm to passengers. By having parts that can crumple, modern vehicles enhance passenger safety remarkably, as witnessed in automotive history with the significant reduction in fatalities in car races when cars were made with such safety features.