And all this time I thought we were talking about a new plastic car and an
old steel car hitting each other. OK so the plastic car will crumple, the
air bags will inflate, and the tank will still be moving after the plastic
is a flat piece of road kill. By using F=MA, lets say F1=F2 is car one and
car two arriving at the same point at the same time and coming to rest , it
follows that M1A1=M2A2. now if M1 is 10 times more than M2, then A1 is 10
times less than A2. This is not valid say if we both hit brick wall, fall
out of the car with or without a helmet, fall down stairs, or whatever.
What I said was if plastic and tank collide, plastic looses. Think
train/car, airplane/mountain, whatever. You both make good points they just
don't apply in the stated case.
Crash
>> If I was going to put you in a box and chuck you down
>> a few flights of stairs, would you rather it be made of
>> half inch iron plate or sterofoam?
>>
>> All that F=MA proves is that the iron crate would
>> be more likely to damage the stairway. It might do quite
>> a number on the building and still look brand new, the
>> same wouldn't be said for the passenger!
>>
>
>Trevor is right. A motorcycle helmet would be useless if made of iron
rather
>than engineered from a material designed to break BEFORE the skull does. I
>remember a motorcycle dealer telling me that a lady had brought a helmet
back
>for refund because her son had wrecked his bike and the helmet had broken
on
>impact. The boy was ok. The dealer had a difficult but successful time
>explaining to the lady that the reason her son is OK was because the Helmet
>HAD broken and had taken up the energy of the impact BEFORE his skull was
>crushed. While the newer cars crush easier and quicker than the old cars,
>the crushing is a feature that absorbs the energy of the impact and
actually
>makes them safer. Especially when part of a system that includes air bags
>and seat belts.
>
>--David C.
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