This thread is getting a little ummm amusing I guess:
First we are presented with the question of the difference between an
idealized head-on collision between two identical, but soft, cars and a
collision between one of those cars and a brick wall
This should be a discussion about energy not momentum AND the Earth should
be included in most of the calculations -- certainly if conservation of
energy is in one's mind.
Then the masses are different then the velocities get complicated then the
cars bounce, hit a tree, or a ditch -- the collision becomes elastic but
the Earth is still ignored. This is still an energy problem, but without
any hope of conservation.
The question has become a moving target! One poster is trying to comment
on one set of propositions -- while another is changing the
propositions. This is a silly way to conduct a class.
NEXT we have people bouncing about and their gizzards under attack -- Where
momentum DOES matter, but people want it to flow about like the wind. This
is getting out of hand.