tiny-tim said:
weight is really only relevant if we are in contact with something (eg the floor) …
we cannot
feel our weight, we can only feel reaction forces between us and other objects
we only "feel" our weight when eg the floor pushes on us with a force whose
magnitude (but not direction) we call our weight
if the floor is accelerating up (eg the floor of a rocket), then the reaction force is greater, so we feel heavier
but in free fall, there is no contact, so nothing to feel

ya,i was thinking this a whole night time==
here i come out an answer:
just like a person stand still on the floor,he has weight because the floor acting an upward force which respond toward the gravity.
F=w(W is the upward force ,we call it Weight)
when you having another force that pulling or pushing like in the elevator
F+w=ma or w-F=ma
when free falling,there are only the gravity force acting .
F=ma
in this case there have no W in the equation ... it seem to be weightless
here i have a question,is the free falling acceleration not relate to our weight?if it is relate to our weight ,then the acceleration will only applicable when Free fall is happening on the surface of earth.
f=GMm assume an mass (m) is 1kg
r^2
the r is radius of earth,we can get the f is 9,81 then using F=ma to calculate the free fall acceleration.that means all our calculation relate to weight are only applicable when the object is on the surface of earth,right? W=m(9.81) ,if it is not on surface of earth,the 9.81 shouldn't be the gravitational acceleration because different radius is using now.
am i correct?
and as my inference,you can really feel if you are free falling,what about the tidal stress?despite i knew that there will be vry vry small and need not to be noticed