# Collision of two identical cars moving in opposite dirrections

1. Sep 28, 2009

### mahela007

What would cause more injuries to the passengers of each car? [no a pleasant example, I know]
a) car colliding against brick wall.
b) car colliding with an identical car moving in the opposite direction at the same speed.

Does it have something to do with the amount of K.E liberated / lost?

2. Sep 28, 2009

### XanziBar

If the amount of kinetic energy lost in both cases is the same (like if it's completely elastic or completely inelastic, for example) then choices A and B are the same. You should also assume the cars are the same mass, there isn't much damage to a semi when it hits a sub-compact.

One of the ways to think about this problem is that in a reference frame at rest you slow down from your initial speed to zero. And in a reference frame moving with one of the cars, you slow down from your initial speed to half of your initial speed. The force you experience in each case is the same.