Re: Weight

[igal@vms.huji.ac.il (Igal Galili)]

Rick,

        >Using the apparent weight (the upwards forces) to define the term
weight
> does have some advantages, but the everyday concept of weight as a downward
> pull would be (in my opinion) harder to overcome than adding the concept
> that we experience that pull primarily through upwards forces and thus get
> fooled in situations where that upwards force does not balance the
> downwards pull of gravity.


        No question, a good point against the "upward weight" is its
oddness for a student.  The force on the support (I define as weight),
therefore is much better, and this is the force which we directly MEASURED
by the spring scale.  Of course, you can not care about this point at all,
but if you want to be in some correspondence to the "scientific method" (as
it is understood today) you cannot discard it as it is crucial.

        The same can be said in regard to your comment about the weight of
astronauts in a coasting satellite:

> I also have no problem with the 'weightless' astronauts--they're NOT.  They
> have no apparent weight but again I harken back to the fact that we
> experience our weight 'normally' through the balancing forces that keep us
> from accelerating.  In the absence of these 'upward' forces they _feel_
> weightless.

        Well, I do believe that you have no problem in this point, but I
bet, many of your students do (let's  say it in other way:  my students
always had ;-) and others too, as it can be seen from research reports).
And if the ONLY way to know that you "have weight" is to successfully grasp
sombody's CLAIM supported with NO local measurament, you might find
yourself  in a striking contradiction with the fundamentals of our
discipline.

Igal.