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Feb19-12, 09:30 AM
P: 8
It gets better. Thanks.

Energy absorbed by car equals its kinetic energy (assuming head-on collision and that both cars stop after), so work done by average force on the car is

[itex]F_{aver}d = -\frac{1}{2}mv^2[/itex]

where d is the deformation of the car.
From 2nd Newton's law the average force is equal to

[itex]F_{aver} = m\frac{\Delta v}{\Delta t}[/itex]

Are these 2 average forces the same?