Quote:
Originally Posted by hypurone
He misstated the effect being equivalent to 2 cars hitting head on at 120mph each. It should have stated as "head on at 60mph each"...
"A head on traffic accident occurs when the front of one vehicle collides with the front of another.
These types of accidents are extremely dangerous because of the cumulative speed affect of
vehicles colliding in opposite directions. Accident reconstruction experts often refer to the
combined difference in speed as closing speed or closing velocity.
For example, if two vehicles collide head on with each traveling at 30 MPH, then the closing speed
between the two vehicles would be equal to 60 MPH. If the same two cars were to collide, with one
of the one of the vehicles stopped, then the striking vehicle would need to be traveling 60 MPH to
equal the same closing speed."
Either way you cut it, it's nasty!  |
No, it simulates 2 cars hitting each other at 120 mph. Or 1 car hitting a sturdy wall at 120 mph. The problem is that two cars (together) travelling at 60 would have half the kinetic energy of a single car at 120, despite the fact that their closing speed is 120 mph.
"For every action, there is an equal and opposite reaction"
In this case, the 'action force' is a car hitting a solid object at 120 mph. The 'reaction force' would therefore be equal in magnitude but opposite in direction ... in other words, a car of equal mass going in the opposite direction at the same speed.
It is also extremely different from hitting a parked car. In that collision, momentum from the first car gets transferred to the 2nd. Usually it is some sort of glancing blow where the first car gets deflected while the 2nd car moves off in another direction, with both cars probably spinning. Both cars absorb a portion of the energy when the impact zone gets crushed, but not all of it.