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1. The problem statement, all variables and given/known data

Seat belts and air bags save lives by reducing the forces exerted on the driver and passengers in an automobile collision. Cars are designed with a "crumple zone" in the front of the car. In the event of an impact, the passenger compartment decelerates over a distance of about 1 meter as the front of the car crumples. An occupant restrained by seat belts and air bags decelerates with the car. By contrast, an unrestrained occupant keeps moving forward with no loss of speed (Newton's first law!) until hitting the dashboard or windshield. These are unyielding surfaces, and the unfortunate occupant then decelerates over a distance of only about 5 mm.

(a) A 50 kg person is in a head-on collision. The car's speed at impact is 17 m/s. Calculate the net force on the person if he or she is wearing a seat belt and the air bag deploys correctly.

7225 N

(b) Calculate the net force that ultimately stops the person if he or she is not restrained by a seat belt or air bag.

1445000N

(c) How do these two forces compare to the person's weight?

F(a) / W =

F(b) / W =

2. Relevant equations

F= ma

Vf^2= V0^2 + 2ax

Vf= V0 + at

x= V0*t + .5a(t^2)

3. The attempt at a solution

This one I have absolutely why my answers aren't checking. I've done all the force work (answers are in red), and for c) the equations are literally given to us. F(a)/ W and F(b)/ W. Now, correct me if I'm wrong, but F(a) is my answer for a) and F(b) is my answer for b). If my person is 50 kg (and weight is measured in kg) then why in the world are my answers not working? ( 7225 /50 and 1445000 /50).

Thanks again!

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# Homework Help: Car Crash numbers not working?

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