Final answer:
The force felt by a car during a collision with a crash barrier that increases the time of impact by six times decreases because the impulse (change in momentum) remains the same while the time increases, thereby reducing the average force according to the impulse-momentum theorem.
Step-by-step explanation:
The question is concerned with the impulse experienced by a car when it collides with a crash barrier. The force felt by a car hitting a crash barrier designed to increase the time of the impact by six times compared to concrete will decrease because the same momentum change is distributed over a longer time period. According to the impulse-momentum theorem, impulse is the product of the average force and the time over which the force is applied. It can also be expressed as the change in momentum of an object.
Since momentum change is constant for both the crash barrier and the concrete wall (provided that the initial and final velocities are the same), increasing the time of the crash will result in a lower average force. This is supported by the equation F = Δp / Δt, where F is the average force, Δp is the change in momentum, and Δt is the change in time. Thus, if the crash duration increases by six times, the average force exerted by the barrier will correspondingly decrease by six times.
To provide an example, referring to the previous question, if the initial force exerted by a solid wall was 740,000 N, and the crash duration is increased by 6 times by the crash barrier, then the new average force exerted would be 740,000 N / 6, assuming all other factors remain constant. The car safety features like airbags and well-designed crumple zones are practical applications of this principle, aiming to reduce the forces experienced by the occupants during a crash by extending the impact duration.