# [urq] Audi A4 bumpers are well rated

LL - NY larrycleung at gmail.com
Fri Aug 17 19:08:21 EDT 2007

```Yes, I know. Straight from the Conservation of Momentum.

Mass A = Mass B.

Here, a well designed small car can fair very well. It's the unequal mass
collision
where the small cars loose. a = F/m where a is the acceleration of the
vehicle,
F which is equal for both vehicles involved in the crash (Newton's 3rd Law)
and
m = the mass of the vehicle being studied. Since a is directly proportional
(same as the 1st equation, re-adjusted to F = ma) to the forces applied to
the
occupant of the vehicle, the more a there is, the worse it is for the
occupant.

Since a 6000 lb Hummer has twice the mass of say a Mini Cooper, the
resultant
occupant acceleration (within limits, I'd bet the crush zones of the Mini
are
better designed, but it's going to be quite close)  in the Mini will be
double that
of the Hummer. So, in an extreme case, say the Hummer experiences 10 G's
crashing into a Mini. 10 G's may cause some internal injuries. The Mini's
occupants
however, will see about 20 G's, which is nearly always fatal. Yes, I know
that
crush zones will decrease this disparity, but certainly not by a factor of
2:1. This
is why the perfectly survivable in a single car crash (barrier, offset
barrier, etc) Mini,
will not fare so well if it is overrun by some wayward SUV, driver yakking
on a
cell phone while pouring coffee, taking a memo, and changing radio stations
at
the same time. So what if they end up wandering into your lane, they'll be
fine!

BTW, the approximate weights (yes, an indirect measure of mass, but since
both cars are assumed to be in the same gravity field at the time of
collision,
so valid) of the vehicles is assuming a moderately loaded GVW, not curb
weight.

After all, we don't drive empty cars.

LL - NY - the Physics Teacher and former Mech Eng.

On 8/17/07, Mike Sylvester <mike at urq20v.com> wrote:
>
> With a single car accident it all depends on what you hit.
> If you hit square on into something that doesn't move, the result is the
> same as a multi car head on with a car of the same mass.
>
> Mike
>
> www.urq20v.com
>
>
> -------- Original Message --------
> Subject: Re: [urq] Audi A4 bumpers are well rated
> From: "LL - NY" <larrycleung at gmail.com>
> Date: Fri, August 17, 2007 9:52 am
> To: "Louis-Alain Richard" <larichard at plguide.com>
> Cc: urq at audifans.com,  quattro at audifans.com
>
> agreed on the size issue, but it does seem that mass seems to come
> with size. FWIW, I wouldn't, in spite of modern design, want to be in
> a multi-car wreck in a Lotus Elise. Single car, okay, multi, NEVER.
>
> Heck, even a Mini is sort of scary these days, and for it's size, it's
> quite a bit heavier than even cars of 20 years ago (my GTi, when I
> was competing Solo 2 Stock, weighed in on the scales (I worked
> impound at that event, so we were bored and scaled our cars) was
> 2201 lbs, with me in it and a 1/4 tank of gas. A Mini weighs 100 lbs
> more, empty.
>
> LL - NY
>
>
```