Re: crash tests

[Kiwi <enzeder@home.com>]

½mV²
Ok, for arguments sake, one car has a mass of 2000Kg (we'll call it
cadillac), and a velocity of 10m/s (36Kph) = 100KiloJoules (I think that's
the right unit).  And that cadillac at 20m/s has 400KJ.
That means a head on collision with another cadillac of similar mass and
velocity has 200KJ Joules to release instead of the 400KJ of one cadillac
at 20m/s running into a parked cadillac (negating any solid barricade
argument).  However, it might be less severe to run into a solid object at
10m/s than a deformable one (eg: car) at 20m/s.  

To recap, 1+1=2, but (1*2)²+0=4.

Make sense?  It's been 10 years...what am I forgetting?

Arryn


At 01:24 PM 12/13/1999 -0500, Huw Powell wrote:
>> Look at the collision as two separate accidents.  One car traveling west
>> (let's say) strikes an obstacle and comes to an almost instant stop from 30
>> mph to zero mph.  A second identical car traveling east at 30 mph strikes
>> an obstacle and almost instantly stops moving.  The change in kinetic
>> energy in each case is KE = (mV^2)/2.  Each car "releases" that amount of
>> energy.  True, the total energy is double because there are two cars but it
>> is spread over two cars, not one.
>
>not one?
>
>> 
>> BTW a single car traveling at 60 mph striking a barricade 
>
>the quote I was agreeing with used two cars, no barricade.  The "non
>moving" object is another car.  the "barricade" example where the
>baricade is immobile is *completely different*.
>
>> releases four
>> times as much energy as the same car traveling at 30 mph would release, not
>> double.  Remember, the energy change is proportion to the *square* of the
>> velocity change.
>
>This I remember.  Now remember your relativity and look at the closed
>system.  Each car is going 60 mph relative to the other one and ends up
>going 30 mph after it hits it.  
>
>> 
>> At 12:00 PM 12/13/1999 -0500, you wrote:
>> >>                 ... Be aware that two cars travelling towards each
other,
>> >> each at 30 MPH is an extremely severe collision, visually, it would LOOK
>> >> like driving into a parked car while you were doing 60 MPH, brakes OFF.
>
>-- 
>Huw Powell
>
>http://www.humanspeakers.com/audi/
>
>82 Audi Coupe; 84 4kq; 85 Coupe GT; 73 F250
>
>http://people.ne.mediaone.net/audi/thoughts.htm
>