I believe the car hitting the immovable wall would be VERY SLIGHTLY worse,
and here's why.
It is correct that the amount of energy absorbed or dissipated per car is
the same in each situation, but the dynamics of the collision are a bit
different. Hitting an immovable wall the car has little choice but to stop
by crumpling straight into the wall. In the two car case, any imbalance in
mass between the left and right sides of a car (and being identical, both
cars would have the same imbalance) would cause some of the energy to go
into rotation of the two cars after the forward motion had been cancelled.
The energy in the rotation would then be dissipated over a slightly longer
time, resulting in somewhat less deceleration.
Since any side to side imbalance in the mass of each car would tend to cause
rotation in the same direction of the combined cars, I believe there would
be much more rotation involved in the two car case. In the wall case, no
significant rotation of the car could take place because the wall is
immovable.
If each car was perfectly balance left to right (and the steering geometry
changes as the cars crumpled did not cause them to spin or glance off each
other) then the collisions would be equal.
Bert Kleinschmidt
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A car hits an immovable wall at 40 MPH.
The same car hits its identical twin car, each going
40 MPH, head on.
Which collision is worse, and why?
Answer tomorrow. First correct answer wins 2 broken
lift-the-dot fasteners and a rusty pitted lifter.
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