[Phys-L] Re: collision question

[Scott Goelzer <s.goelzer@COMCAST.NET>]

If "damaging" refers to the injury the passenger in the car experiences
due to acceleration, then why would these not be identical situations?
If car 1 going a given speed is brought to rest by crumpling a given
distance because of car 2, then the same acceleration should occur for
hitting a wall since the speed and the distance are the same.

This problem was given as an example to the solution of the Levi's
Horse problem in Epstein's "Thinking Physics"  book.

If "damaging" refers to insurance costs, then two cars and passengers
were damaged vs one.

I have heard (third -hand) that many drivers ed. teachers explain that
two cars colliding at 30 mph is the same at one car hitting a wall at
60 mph. The squared term in the KE equation seems to make this
impossible.

Scott



**********************************
Scott Goelzer
Physics Teacher
Coe-Brown Northwood Academy
Northwood NH 03261
603-942-5531e218
sgoelzer@coebrownacademy.com
**********************************


On Feb 17, 2005, at 8:53 AM, Ludwik Kowalski wrote:

> Assuming stopping times are the same a head-on collision of identical
> cars has more kinetic energy available than the collision of one car
> with a cement wall.
>
> Ludwik Kowalski
> Let the perfect not be the enemy of the good.
>
> On Thursday, Feb 17, 2005, at 08:34 America/New_York, Kilmer, Skip
> wrote:
>
> > I'd guess the wall, since cars are now designed to have frontal crush
> > zones that would tend to increase the collision time.
> > skip
> > > Which would be more damaging, driving into a very massive concrete
> > > wall
> > > or having a  head-on collision with a similar car moving toward you
> > > with
> > > the same speed?