What Was the Driver's Average Acceleration During a Collision?

[High_Voltage]

Homework Statement

A car traveling 85km/h strikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80m. What was the average acceleration of the driver during the collision? Express the answer in terms of "g's" where 1.00g = 9.81m/s^2.

Homework Equations

(85 km/h)(1000m/1km)(1h/3600s)= 23.6m/s

(vf^2-vi^2)/(2d)=a

The Attempt at a Solution

vi=23.61m/s
d=.80m
vf=0m/s

(0^2)-(23.6^2)/(2x.80)= -348.39m/s^2

-348.39/(9.81)= -35.51g's 35.5g's in the negative direction.

This does not seem right to me, can anyone confirm or lead me in the right direction, not do the work for me as I know that is frowned upon here =)

 

[zhermes]

Looks right. Thats why accidents suck.