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On 11/18/2003 09:09 PM, Ludwik Kowalski wrote:
. . .> c) Why should a static force experienced by a
> person on a floor (it has the same magnitude
> as m*g) be replaced by the "flow of momentum."
> Is this concept less mysterious that the concept of
> force? In which direction is the momentum flowing?
Contact contributes a flow of upward momentum across
the floor/person boundary into the person. That is,
we have +Z flow of +Z momentum. This is of course
trivially equal to -Z flow of -Z momentum.
Meanwhile gravitation contributes a +Z flow of -Z
momentum. I don't associate this with the
floor/person boundary; rather it flows into each
molecule of the person independently.