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Re: Fwd: Audi A8 Achieves Highest Possible Safety Test Rating

Michael Williams <daserde@ucla.edu> wrote:

> Im confused now.  Wouldnt the momentum of the two cars add together
> and cause what would be equivalently a 70 mph collision?  What am i 
> missing...its been years since my last physics class...

Yes, the relative speed of impact is twice at 70mph.  But the energy
absorbing material is also doubled, so the net effect is that as far as
each car is concerned, they feel just like if they had crashed into a
stationary wall at 35mph.

However, if one car is heavier than the other and with a stiffer front
structure that doesn't absorb a lot of energy (full size pick up truck
comes to mind), the smaller and lighter car will take a much harder
blow.  Not only is the amount of energy absorbing material (crupple
zones) reduced and there is more energy to absorb, but the lighter car
will decelerate a lot quicker than the big car.  Net result:  the pick
up truck feels like it had a 20mph collision with a wall, while the
small car feels like it had a 50mph crash.

Now, if it was the pickup truck crashing into a wall, the driver would
feel an impact twice as big as the driver in the small car because all
the force of impact is transfered to the ocupants.  Yes, our Audis are
designed to sacrifice themselves to save our lives, not to escape
undamaged with a dead driver.

Luis Marques
'87 4kcsq