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Hmmmm...I am still missing something.
I am not considering only something which is the abstract concept called
"center of mass",
I am referring to the parameter in question, called "location".
I find it expedient to embody the (still somewhat abstract) concept of
"location"
in the concrete observable called the position of the two feet on
which the subject is standing.
I next visualize the effect of the subject's thrusting both her arms
horizontally forward.
This moves the position of the subject's feet (in order to keep the
center of mass unchanged).
I further visualize the frictionless surface on which she stands as
concave spherical, in order to
replicate the characteristic energy transfer between potential and kinetic
which we observe on a swing.
Having obtained this small initial uphill displacement - the location
of the feet, I am willing to
suppose that a three year old could then maneuver her arms at the
appropriate frequency
so as to puimp up the amplitude of the initial oscillation.
Where do I err, I wonder?
:-)
Brian W
chuck britton wrote:
If there is absolutely NO static or kinetic friction - then the CM of
the you+cardboard cannot move.
If there is a touch of static friction - then any three year old can
easily cruise across the room.
On Feb 9, 2009, at Feb 9(Mon) 7:28 , Brian Whatcott wrote:
Stefan Jeglinski wrote:
I hope someone disembarasses me soon of what seems to be the obviousHere is a somewhat analogous situation. You are standing on aIs that a euphemism for frictionless, I assume?
large sheet
of cardboard on a perfectly smooth floor.
Take the cardboard as massless.Stefan Jeglinski
Can you change your location on the floor?
response,
which is.... Yes, Of COURSE you can change position.
Brian W
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_______________________________________________
Forum for Physics Educators
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https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l