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2 Answers 2

Yes, it's also known as a spring.
It's no different from the energy absorbing buffers on a train or rubber bumpers on a truck.

Cars are designed to absorb a lot of kinetic energy, rather more destructively, by the front of the car crushing and collapsing

It doesn't disable intertia it simply increases the time over which the car contacts the fixed object and so slows it more gradually and so imparts less force on any objects inside

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In the movies that are shown here, the translational kinetic energy is passed on to a big rotating cylinder in the form of rotational kinetic energy. (The second movie is the clearest with that respect, in the first movie it is only mentioned)

What you're seeing in the movies, is that some sort of pin is installed at the front, which uses the force during the impact to accelerate the cylinder in the car. This reduces the force on the bottle, which therefor does not brake.

However, I have to remarks here: 1. You need a pretty large (heavy) cylinder to make this really feasible. And it only works during frontal collissions. You will never see this in real cars. 2. In the second movie, they first hit the bottle with the modified car, and then with the non-modified. Maybe there were some cracks already, making it very easy to brake the second time.

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I too noticed the differences between EPAR on and off. As for the cylinder size, prof. Stanislaw Gumula states, that for a car, device of size 20x20x20cm is sufficient: The article is in polish but google translate works quite well. – Jupan Jan 15 '12 at 20:50
(20 cm)^3 is 8L. Suppose it is lead, then this will be close to 100kg, quite large to only help for collissions in one direction. – Bernhard Jan 16 '12 at 6:49

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