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certainlyI should point out that free-fall frames are not inertial frames in
Newtonian physics.
...
They weren't able to be recognized as such by Newton, but they are
recognized as such in 20th century Newtonian physics. I use that term to
refer to the very accurate Newtonian approximatian to GR that works so well
in the weak field of the solar system.
...
I'm curious, how many force vectors does Marlow draw acting on the cube
(book) when he explains Newtonian mechanics to introductory students?
...
Then attach the spring scale directly to the cube. It would still show
exactly the same thing -- attached to one side (what I called "up") the
scale would stretch, and you can see both the amount and the direction
of the force you have to apply to the cube to keep it from accelerating
relative to your lab. On the opposite side of the cube you would have to
push in the same direction by the same amount to do the same thing.
am>Now I am truly and totally confused. If spring balances work by...
.... The integral to the centrifugal force dot dx will equal my
change in kinetic energy...
Not in any physics that I know, unless you put in "zero" as the
value of the centrifugal force, which of course will give you the
correct zero value of change in kinetic energy (as a dynamic quantity,
kinetic energy has a simple relation to acceleration or velocity ONLY
in inertial frames).
.......of
The problem with the above viewpoint is that it reduces dynamics to
kinematics; while OK mathematically and doesn't lose the self-consistency
the theory. (Marlow and I get the same numerical answers to problems)
As far as I can see, we don't at all get the same answers for any
dynamical quantities such as energy, work, momentum, mass.
as
... Once I'm in contact with the
door handle the none of the forces present are doing any mechanical work
my kinetic energy isn't changing (nor is my velocity vector changing
direction! in this frame of reference; ...
True, your velocity relative to the noninertial frame of the car is no
longer changing, but real work is being done, real bruises are being left,
and your kinetic energy is changing, and infrared detectors will detect
the dissipation that must accompany real physical processes.