The front 1.20 m of a 1500 kg car is designed as a "crumple zone" that collapses to absorb the shock of a collision.

(a) If a car traveling 22.0 m/s stops uniformly in 1.20 m, how long does the collision last?

(b) What is the magnitude of the average force on the car?

(c) What is the acceleration of the car? Express the acceleration as a multiple of the acceleration of gravity.

(Conservation of energy is unlikely to help as in such cases as much enegey is lost in generating heat etc.)

Use formula v^2 - u^2 = 2 fs

0 - 22^2 = 2 f 1.20

acceleration = f = - 22^2/2.40

Force = mass times acceleration

And for part (a) you can use
x = (Vo + Vf)*t/2
where x is distance, Vo is original velocity, Vf is final velocity, and t is time - your unknown. Note: (Vo + Vf)/2 is average velocity, so when you multiply that by the time to stop, that's the distance traveled.