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[Phys-L] Re: Momentum Again



I don't really understand the following:


|
| If we start from the reference of the center of mass of the
| planet Earth, then there is no kinetic energy on Earth.
|
| Or if it were possible to assign a center of mass of the Universe,
| there would be no kinetic energy in the universe.
|

The calculations that I am familiar with say that the kinetic energy of
a system is the KE due to the c-of-mass motion plus the KE of the bits
and pieces relative to the c-of-mass. So in the c-of-mass frame one
still has a non-zero portion; namely the KE of the bits and pieces
relative to the c-of-mass.

(Unless I misunderstood the intent of the above quote, which is quite
possible.)
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