[tuccillo]

You are working from the assumption that a wall has the same mass as a golf cart.

Originally Posted by Polar Bear

"same effect"...because you say it is so that makes it so? Pretty big assumption there.

How about this...
Scenario 1 - A wall is moving along at 20 MPH and hits a stationary wall.
Scenario 2 - Two walls are moving toward each other, each going 20 MPH, and collide.

The intensity of the impact for both scenarios is exactly the same? I don't think so. Now do you understand?

Look, I know what you're saying. And I don't disagree with you as much as it might appear. The problem is we're comparing apples and oranges. One has walls with zero energy absorption. Another has vehicles with who-knows-how-much energy absorption. But comparing the two is similar to saying the damage of two vehicles colliding head on is similar to one of them driving off a certain height cliff, or being near an explosion, or something else...again...apples and oranges.

Relative velocity at impact is the velocity that matters in a collision. After that is when you start considering other factors such as energy absorption, energy distribution, etc.