Re: gravitational sensations--was Work/Energy theorem ?

[Leigh Palmer <palmer@sfu.ca>]

I never interpret or teach the upward force of the ground as my weight!
I can't think of a more confusing interpretation. I teach my students
that weight is the force of gravity which acts downward on everyone.
It even exists in free fall when considered from an inertial frame of
reference outside Earth. It is erroneous to speak of such a frame as
exhibiting "weightlessness" when considered from an inertial frame. It
is the force that keeps the Shuttle astronauts from flying away from
Earth. Weightlessness is apparent in their frame of reference.
Observation over an hour or so of the motion of an apple placed at rest
somewhere other than at the center of mass of the shuttle over an hour
will readily demonstrate to the astronauts that they are not in an
inertial frame, though they will still feel weightless.

Leigh

> We all experience the ground pushing up (or in my case the chair in front
> of this computer pushing up).  But we _tend_ to interpret these upwards
> forces as our 'weight'.  While in one sense these forces ARE our weight
> since we really don't directly experience the gravitational force without
> them, in most introductory sequences we define weight as the gravitational
> attraction of a large body (like the earth) for smaller, nearby object,
> such as ourselves.  Ultimately it is this confusion that leads us to call
> the sensation in certain accelerating frames, 'artificial gravity'.
>
> Rick
> ----------
> > From: Leigh Palmer <palmer@sfu.ca>
> >
> > One of the correspondents in this group can feel the ground pushing
> > up on him through an organ in his middle ear. I feel that must be
> > the case or else he would be unable to walk with his eyes shut.