the question is this:

suppose you want to design an air-bag system that can protect the driver in an head-on collision at a speed of 100 km/h. estimate how fast the airbag must inflate to protect the driver-- I GOT THE CORRECT ANSWER TO THIS ONE ALREADY. now the second question is--
assume the car crumples over a distance of about 1 meter. How does the use of a seatbelt help the driver? --- Can someone plz tell me what this one would be? Im lost? Btw, I appreciate any help, thanx. =)

3 answers

Without the seat belt, the air bag must exert almost all of the force on the driver to decelerate him/her. Without a seat belt, the driver will have a higher force exerted on his/her head, may hit the windshield, or be thrown to an area that is not protected by the air bag.
this answer is correct but i need the mathematical law needed to solve this problem.
There is no single law to quote that explains why it is important to wear a seat belt even when an air bag is present. It is a question of keeping the person behind the air bag and distibuting the decelerating force between the seat belt and the air bag.