Miata Mailing List: December 1995, Message #191
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   From: kjwalker@freedom.rsoc.rockwell.com
Subject: Re: Collision Closure Speed
   Date: Mon, 4 Dec 1995 14:43:30 -0500

     Richard D. Buhl says:
     ----------------------------------------------------------------------
     Now if car 2 is a truck weighing in at 20 tons then M2 = app. 18000 Kg 
     and still going west at 50 mph then:
     Mf=1000+18000= 19000
     and
     M1*V1 + M2*V2 = MfVf
     (50)*1000 + (-50)*18000 = 19000*Vf
     then Vf = -44.7
     
     Which means that the speed after crash will be 44.7 mph going west.  
     This would be equivilant (sort of) to car 1 (miata) hitting a brick 
     wall at 94.7 mph.
     ---------------------------------------------------------------------
     
     All of this makes perfect sense if you think of it in a two step 
     process:  
     
     1) Miata goes from 50 to zero in less than a second.  Add to that step 
     two in which:
     
     2) Miata accelerates from zero to 44.7 inside of the same second.
     
     Indeed, with Richard's calculations (from formulas I was *way* to lazy 
     to go look up in my old physics book) we can finally put this thread 
     to rest!  ?
     
     kjw &
     TIC-TAC