Question

Which results in a higher force of impact? Assume both collisions are completely inelastic (your car comes to a stop) and both take the same amount of time.


A) Running your car at 20 mph into a solid wall
B) Running your car head-on at 20 mph into an identical car also driving at 20 mph in the opposite
direction
C) The forces are equal

The answer is C but I don't understand why. Can someone explain this to me?

Answer 1

Force equals mass times acceleration...the mass of your vehicle is the same, always. The acceleration is also to be considered the same for both problems. So if both equations, (one for collision with wall, and one for other car) have the same numbers, then the forces are equal. Another way to look at it is to think about the collision itself: what is the speed at the point of impact? It is the same regardless of what object you hit, a wall, a car, or a semi truck...zero.