Quote:
Originally Posted by DGthe3
You are correct in that two cars can absorb twice the energy. But they'll also have twice the energy at impact, so it cancels out.
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Keeping in mind that E = mc˛, I'd say the energy of two moving cars would be about 4 times the energy as one car moving and an object in rest, hence why they refer to it as the equivalent of two cars travelling at 120mph, I believe... (which brings it to, as the Mythbusters link also shows, double the force, because of the fact that the cars can absorb double the energy of one car and a non movable object, effectively dividing the energy over the mass of the two cars).
Either way, it's pretty simple.... crash into a car at 120mph (be it both moving or not) and you'll not walk away because of the immense G forces at work during the deceleration... (and that is, I believe where the "crumple zones" actually start doing their work, by dividing the energy during the transition from moving to standing object).