Velocity of Head from Car Accident

[KateinChicago]

My friend was in a head-on collision this week. They were traveling approximately 35 mph. A car collided with them head-on traveling at approximately 30 mph. The airbag deployed, and the impact caused a tremendous contusion on my friend's forehead, but no skull fractures. It's been years since I've had physics, but I was wondering how much force (roughly) was "applied" to my friends forehead to cause his blunt-force trauma injury? The two cars were smaller-sized sedans (not compact cars or SUVs). There would be the velocity of the cars traveling toward each other, the force of their impact, the velocity of the airbag deploying, and the force of its impact, and then there's the velocity of my friend's head whipping foreward toward the airbag. I'm sure this is an easy calculation if I knew exactly what to imput. Thanks!

 

[jack action]

Surf around on this http://hyperphysics.phy-astr.gsu.edu/HBASE/carcr2.html#cc1".

 

[russ_watters]

It's really not an easy calculation and you can forget about the speed of the cars: the airbag deploys extremely fast, but is light and should be just about fully deployed when you it/it hits you, so it hits you with a very large force for a very short time. The time of the impact between the airbag and your forhead is so short that it never transmits to your brain - it stops at your skin. Basically, your skin stops the airbag very quickly, then the pressure of the air inside the airbag stops your head in a much longer time.