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[Phys-L] Re: Momentum



Clarification: the amount of energy doesn't change -- just the
percentage. So, my post should've read...how does nature know exactly
how to change WHAT FRACTION of energy is lost when viewed in a different
frame?

____________________________________________________
Robert Cohen, Chair, Department of Physics
East Stroudsburg University; E. Stroudsburg, PA 18301
570-422-3428; www.esu.edu/~bbq

-----Original Message-----
From: Robert Cohen
Sent: Tuesday, December 06, 2005 12:44 PM

And even more amazing...how does nature know exactly how to
CHANGE how much energy is lost when viewed in a different frame?

-----Original Message-----
From: David Abineri
Sent: Monday, December 05, 2005 7:55 PM

In the ideal case of two equal masses colliding linearly
where one is
stationary and one is moving whereby they stick together after the
collision (totally inelastic), the conservation of momentum
leads to
the conclusion that half the kinetic energy is lost to
other forms.
Of course, in the real world, one has sound, deflection of
materials,
friction at least that will convert the energy to other forms.

But what does this really say? What do the "ideal" conditions mean?
Why, regardless of the masses is exactly half of the kinetic energy
lost. When we say "ideal" conditions to we mean
frictionless, rigid
objects in an airless world?

Can someone help make some sense out of this? I wish I
could make the
question more clear so perhaps it is my lack of clarity about the
situation that is the cause of the question. Any help in clarifying
this issue would be appreciated. David Abineri
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