[MR] Heavy Helms and inertia

[Teleri Barod]

--- thumpa at mindspring.com wrote:
> 

> 
> Close... actually F=MA is mass times acceleration.  
> Or you could say Force = Mass times Velocity squared
> 

Milord?  I don't recall this one.  dv/dt isn't the
same as v^2.  In fact, if your velocity is constant,
the net force on an object must be zero, as there is
no acceleration at all - even if the velocity is
large.

Perhaps you were thinking of kinetic energy = 1/2 *
mass * velocity^2?

I think the momentum argument is the most compelling
for the heavy helm case.  My guess is that lighter,
more modern head protection uses energy dissipation
(the feather pillow one fellow mentioned).  The energy
of the blow goes into deforming the high-tech foam and
plastic of the helmet rather than your head.  Aren't
such helmets usually replaced after a serious blow? 
I'm fairly sure this is the case with motorcycle and
bicycle helmets, and less sure for football gear.

I think, for what we do and how hard we hit, a heavy
steel helm is most practical and safe.



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