Answer
The acceleration is $2800 ~m/s^2$ which is around 280 g's.
The force felt by the 68-kg occupant is $1.9\times 10^5 ~N$.
Work Step by Step
$v = (35 ~\frac{km}{h})(\frac{1000 ~m}{1 ~km})(\frac{1 ~h}{3600 ~s})$
$v = 9.722 ~m/s$
$a = \frac{v^2-v_0^2}{2x}$
$a = \frac{-(9.72 ~m/s)^2}{(2)(0.017 ~m)}$
$a = -2779 ~m/s^2$
$a \approx -2800 ~m/s^2$
The magnitude of acceleration is $2800 ~m/s^2$.
Next, finding the number of g's:
$\frac{2779 ~m/s^2}{9.8 ~m/s^2} \approx 280\times g$
Now finding the force felt by the occupants of the car:
$F=ma$
$F = (68 ~kg)(2800 ~m/s^2)$
$F = 1.9\times 10^5 ~N$
