Two identical cars, X and Y, each moving at the same speed on a level road, crash into identical rigid barriers and come to rest. Car X stops in 0.050s, whereas car Y, which has a crumple zone, stops in 0.10s. Which statement best describes the magnitudes of the average net forces exerted on the cars during their respective collisions?
a) The average force on car X is twice that on car Y, because X stops in half the time.
b) The average forces on the two cars are equal, because both cars undergo the same change in momentum.
c) The average force on car X is half that on car Y, because X stops in half the time.
d) The average force on car X is four times that on car Y, because kinetic energy depends on the square of the speed, and X gets rid of this energy in half the time.