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These concepts can be confusing to kids.
I believe that Einstein's happiest thought was that if a person jumps off
a cliff (no air), then she has no sensation of weight. This led to his
general theory of relativity.
True weight is mg, while apparent weight is given by a bathroom scale,
which shows the upward support force. Jump off a cliff, and that scale
reads zero. You have no apparent weight, just like those floating
astronauts in the orbiting shuttle. Plenty of true weight. You can also
hang a wood block with a spring scale. Release the block and it falls due
to its true weight. But the scale reads zero while the block falls.
Scale can also be used with fluids. Suspend a 1-kg mass from a spring
scale. It weighs about 10 N. When completely submerged, the scale reads
about 9 N. The difference is the buoyant force. So the buoyant force is
abut 1 N -- the weight of water displaced (which can be measured).
Kids understand these true weight/apparent weight ideas using these scale
activities and their applications.
Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu> writes:On Nov 8, 2010, at 8:40 AM, Scott Orshan wrote:
I'm fine with that definition. Now can we get the astronauts to stop
telling everybody that they are weightless, and in Zero G?
But, with that definition they *should* be saying that they are
weightless.
"... the weight of a mass M in a specified frame of
reference is M times the free-fall acceleration in that specified
frame of reference."
John Mallinckrodt
Cal Poly Pomona
_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l
_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l