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The Earth's surface is an accelerated frame. You must look at pucks
supported on an air table in a horizontal plane to see momentum being
conserved. That is because the momentum of objects free to fall near
Earth's surface is not conserved; they tend to gain momentum downward
due to the presence of an acceleration of the frame upward with
magnitude g. In a plane perpendicular to this acceleration, a
horizontal plane, momentum is conserved. In the space shuttle one
would not need to use an air table to demonstrate conservation of
momentum. One could collide tennis balls floating weightlessly in the
air just as well, easier to do, and with a lot less attendant noise!
"The" frame of reference of that rotating camera is very complicated.
At each point in its frame there will be an acceleration given by the
sum of the Earth's surface acceleration (the camera is attached to
Earth) and the centrifugal acceleration at that particular point.
Remember, one must always work locally. The relations work for only a
small region around the point of interest. The rotating camera frame
is not one frame; it is many different frames. "Horizontal" means
perpendicular to the local direction of the frame's acceleration, and
there are many different "horzontals" in the camera frames. In
addition to that, it is the case that the pucks will be moving in
horizontal planes in *none* of those rotating frames, so one will not
expect to find their momentum conserved anyway!
Leigh