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Re: COLLISION

On Fri, 26 Nov 1999 09:37:18 -0500
David Abineri <dabineri@CHOICE.NET> wrote:
When a moving railroad car collides with a stationary car
of equal mass
elastically, the one car stops and the other begins
moving with the same
velocity as the first.

If they now collide inelastic ally by coupling together,
half of the
kinetic energy of the system is lost.

The velocity of the combined system will be halved.

KE(System) = KE(Car1) + KE(Car2)
In the elastic collision, KE(Car2 - init) = 0 and after is
nearly equal to KE(Car1 - init) (Taking into consideration
increases in thermal energy, ...) while KE(Car1 - final) =
0. Total energy of the system is conserved.



In the inelastic collision, KE(Car2 - init)= 0, but KE(Car2)
is increased to nearly 1/2 KE(Car1 - init), while KE(Car1)
is decreased to 1/2 KE(Car1 - init).

KE(System - init) = KE(Car1 - init)
KE(System - final) = KE(Car1 - final) + KE(Car2 - final) +
('other' energy increases)
= 1/2 KE(Car1 - init) + 1/2 KE(Car1 - init) + other
= KE(Car1 - init) + other
= KE(System - init)

Total energy is conserved.