On Wed, 12 Oct 1994, David Schwarze wrote:

> William Abbott writes:
> Question:  Which is more likely to cause injury to a driver:
> 
> 	A.  Driver runs car into a brick wall at 50 mph
> 	B.  Driver has headon collision with another car going 50mph 
> 	    (combined speed 100mph)
> 
> Assumption and hint: The wall is made out of steel with bricks painted
> on it and will not move or absorb 
> 
> Answer:  neither is more likely to cause injury.  Reasoning: in case B
> there are *two* crumple zones and each absorbs half of the energy.  If
> you have trouble picturing this, just imagine if both of the cars in
> case B ran into a wall from opposite sides simultaneously.  Looks like
> 2 x case A, doesn't it??  :)

So long as both cars have the same mass... Yes.  If not, then the impact 
is divided up with the larger not being affected as much.  (if a bug hits 
your windshield for example)

> Here's another question, but please don't answer it on the list.
> Say you're on a boat in a lake.  You have an iron cannonball in the
> boat with you.  If you were to throw the cannonball overboard, would
> the water level of the lake go up or down?? 

I'll keep it brief.  Sorry for not e-mailing it but others might not know 
either.
The Iron ball is denser than water there for when thrown overboard the 
water will rise with the volume of the ball.  However when in the boat, 
it is forcing the hull of the boat into the lake displacing more than 
it's own volume because it's denser than the water.  If you dumped a 
gallon of water overboard the boat would merely displace one less gallon 
of water with it's hull.  One gallon of iron would weigh more though and 
there fore cause the hull of the boat to be deeper in the first place.
Sorry, that wasn't very brief.

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