posted by Natalie .
A person who is properly constrained by an over-the shoulder seat belt has a good chance of surviving a car collision if the deceleration does not exceed about 30 "g"s (1.0 g= 9.8m/s^2)
Assumind uniform deceleration of this calue calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 60 km/h.
U^2 = 2*a*s
s = U^2/2*a = (16.66)^2/(2*30*9.8)
= 0.47m or 47 cm