Re: [Phys-l] Weightless

["Anthony Lapinski" <Anthony_Lapinski@pds.org>]

People in their everyday experience think a bathroom scale measures their
downward weight. And so when the scale reads zero for the astronauts, they
think g = 0! Lots of confusion and misconceptions with this with ALL
people.

I guess one could never have a true weight equal to zero unless you are
"very far" from all objects (so that g = 0).

We as teachers will never reach any consensus on this topic. What works
for one might not work for someone else. To me, bathroom scales are common
devices, and very useful for illustrating ideas about free body diagrams
in elevators, N3L for objects colliding, and "apparent" weightlessness.

Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu> writes:
> But if an astronaut isn't "weightless," then what is?  Isn't the word  
> of absolutely no use if we can't apply it to astronauts?  Weight  
> implies "heaviness" and heaviness implies (to me) a tendency to stay  
> "pinned by gravity" to some surface.  If a person (or thing?) finds  
> that she (or it?) has absolutely no such tendency, then it seems to  
> me that she has every right to say that she is "weightless" and that  
> we ought to agree with and abide by her assessment.
>
> There's certainly no problem justifying any of this from a Newtonian  
> viewpoint.  It's simply a matter of deciding what you want to mean by  
> "weight."  I don't see any good reason to require that it mean the  
> same thing as "gravitational force."  Indeed, it seems to me a  
> genuine disadvantage.
>
> Anthony Lapinski wrote:
>
> > I agree. This is why I discuss bathroom scales and apparent weight. If
> > someone says there is gravity acting on the astronauts AND they are  
> > also
> > weightless, it ads to more confusion...
> >
> > [Rick Tarara wrote:]
> > > In the 'g' thread, we've (yet again) opened up the definition of  
> > > weight
> > > debate.  While I see certain pedagogical advantages to either of  
> > > the two
> > > main approaches, I would ask if the proponents of saying that one IS
> > > weightless while in the space station can explain that from a  
> > > Newtonian
> > > viewpoint?  Seems to me that there is only one force acting on the
> > > person.
> > > If we call that the gravitational force due to the earth, then what
> > > (again
> > > in the Newtonian viewpoint) is weight?  Isn't this gravitational  
> > > force a
> > > component of your weight?  But it is the only component here in the
> > > Newtonian view and is not zero!
>
> John Mallinckrodt
>
> Professor of Physics, Cal Poly Pomona
> <http://www.csupomona.edu/~ajm>
>
> and
>
> Lead Guitarist, Out-Laws of Physics
> <http://outlawsofphysics.com>
>
>
>
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