From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: Re: Okay, it's not the inverse sprinkler problem...
Date: 18 Jan 93 22:41:30 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Distribution: sci
Organization: SCRI, Florida State University

Regarding the problem of what to do if someone is going to hit you 
from behind: 

First, the false assumption is that you might have time to do something. 
Unless you make it a habit to look in the mirror whenever you hit the 
brake, I do not think you will have time to do much of anything by the 
time you realize you will get hit, if you see the car coming at all. 
Not a lot of time available to you in an accident situation.

I actually have experience with this one -- I was driving an MG when it 
got rear-ended by a Plymouth Fury and driven into a Ford Country Squire 
station wagon.  The clutch was in at the time, free wheeling at about 
10 mph (situation: 2 lane state highway, someone had just turned into 
a driveway and backed up traffic was starting to move; rain slicked 
road surface).  While you think about the answer to this question...

        -----------------  

In article <1993Jan12.160756.14894@linus.mitre.org> m14494@mwvm.mitre.org (Mike White) writes:
>Mark Schnitzius writes:
>> At first it seems that "hitting the clutch" would be the
>> proper answer, so your car would provide the least resistance
>> to the oncoming car.  But consider -- shouldn't your goal
>> be to reduce the sudden acceleration that you will be 
>> experiencing?  If that's the case, then maybe hitting the
>> brake would be the correct answer.

Yes, acceleration is the correct word here.

Truly remarkable acceleration.  I thought for an instant that I had 
popped the clutch with a 457 under the hood of that MG. 

>It might be, if your car was incompressable.  In fact, most of
>your injuries would probably stem from deformation of the car, and
>subquent crush injuries and rupture of the gas tank and fire/explosion.
>You did't give enough information to answer the question: is the car in
>question a Volvo or a Pinto?

No.  Injuries are caused by secondary impact between the driver and some 
part of the interior of the car.  The crushing of the car is your friend, 
particularly in modern vehicles designed to do just that -- although 
mainly in the front and back.  If you have your belts on so you are 
conscious, there is plenty of time to get out of the car, although it 
is possible for the car to twist up and trap you.  

               ---------------------

Back to our little experiment.  The damage was as follows:  I think the 
Fury had a scratch or some of our paint on his front bumper, and we bent 
the trailer hitch on the station wagon.  The MG was totaled, but mainly 
because it was not worth much to begin with.  Its gas tank fell off when 
the impact caused the rusted straps to break, and the front and back were 
caved in about 6 inches.  It was close to an elastic collision. 

Injuries were more interesting.  The driver of the Fury was unhurt, as 
well as being well known to the local police for driving a bit too fast. 
The two of us in the MG were badly shaken but unhurt, although I think 
I had a minor whiplash injury.  I was protected by the *low* seats of 
that old MG, so the whiplash was taken up by most of the upper half of 
my back.  My passenger, the car's owner, was asleep and slumped down so 
the seat back took all of the impact forces.  The driver of the station 
wagon had to be taken away by ambulance.  His headrest was down, like 
it is in most people's cars, so that the top was just below the bottom 
of his skull.  His whiplash was concentrated on a few vertebrae, and 
he was in much pain.  None of his passengers, including kids riding in 
the back of the wagon, were hurt, so in this case a minor impact caused 
serious injury just because of the geometry of the secondary collision. 
(His shorter wife was probably protected by her headrest.) 

--
J. A. Carr                                    |  "The New Frontier of which I  
jac@gw.scri.fsu.edu                           |  speak is not a set of promises
Florida State University  B-186               |  -- it is a set of challenges."
Supercomputer Computations Research Institute |   John F. Kennedy (15 July 60)
Newsgroups: sci.physics