From: Kai Becker (kmb@kai-m-becker.de)
Date: Sun Feb 09 2003 - 06:07:01 MST
Am Samstag, 8. Februar 2003 22:23 schrieb Edwin Evans:
> When a vehicle crashes, its size is the attribute of the vehicle that
> most affects the occupants' injury risk.
That equation has more variables. F1 racing cars show that humans can
easily survive crashes with >200km/h in rather lightweight constructions
(carbon fiber, aluminium, etc.), even if they drive into the sideline.
The energy of the impact is used to crush and crumple everything else but
the drivers cell.
> If cars of the same mass crash into each other, each will undergo
> identical speed changes.
That's true, but says nothing about the effect of the crash on the
passengers. A crash is an exchange of energy. The real scenario is not
only determined by the masses of the two bodies, but also by their
relative velocity to each other, the form of the bodies and the way the
energy of the impact is distributed.
Your own article says it: "However, the risk decreases as the common mass
of the vehicles increases [...]. This effect is not because of the mass
but because heavier vehicles are generally larger. The large size
provides more crushable space and therefore more time for the occupants
to decelerate."
That's it. Its structure that matters, not mass. What is more efficient
for chopping wood, an iron axe or a wooden club of the same mass? Hitting
along the fibers or across? Why can a small bullet go through a steel
plate, but not through a ligher Kevlar vest?
To look on mass alone seems to be one of the positive feedback loops
which normally lead to unwanted extremes. "Always drive a heavier car
than the others" would probably lead to everyone driving a tank and
therefore outweight the safety with several other disadvantages - e.g.
heavy protective gear for pedestrians...
Kai
-- == Kai M. Becker == kmb@kai-m-becker.de == Bremen, Germany == "Any technology distinguishable from magic is insufficiently advanced"
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