MythBusters - Crash Force - awesome test
 

Video - MythBusters - Crash Force

Mythbusters crew decided to revisit an old myth that was drawing the ire of the show's fans for quite some time. And it's sure to be an interesting topic to automotive enthusiasts.

When two cars collide, each traveling 50 miles per hour, does the resulting force equal one car hitting an immovable object at 100 miles per hour?

It seems like such simple physics, no? But don't forget Newton's third law. To quote the great Wikipedia of knowledge, "Whenever a first body exerts a force F on a second body, the second body exerts a force −F on the first body. F and −F are equal in magnitude and opposite in direction." Or, more simply, for every action there is an equal and opposite reaction.