A1200 kg test car is traveling at 25 m/s when it crashes head on into a wall and comes to a stop. if the time of impact is 0.04 s, what is the force acting on the car?

Force is the rate of change of momentum.

Initial momentum = 1200 kg * 25 m/s = 30000 kg-m/s

final momentum = 1200 kg * 0 m/s = 0 kg-m/s

Force = rate of change of momentum

= (0-30000)/0.04  kg-m/s^2

=750,000 kg-m/s^2

=750  kN

NOTE: Please, in the future, ask the question within the correct subject.  In addition to having better chance of getting correct answers rapidly, your question will be seen by more users with the same interests.