Re: [Phys-L] Nice question on buoyancy and balance

["John Clement" <clement@hal-pc.org>]

Do it in a space suit!  But what if you land on the scale when expiring?

The Minds on Physics series has a wonderful ranking task with a similar
question.  The students have to rank the normal force exerted by a table
onto a box according to various conditions.  The pictures show mostly the
same size medium box, but a few are bigger or smaller and the mass is said
to be proportional to the size of the box.  One pictures shows the medium
box on the table, but another shows the same box with the table deformed.
There is also one showing the medium box inside a bell jar with the notation
that it has a vacuum.  It also has a  medium box with an obviously loose
string attached to the ceiling, one with a small box on top of the medium
one, and one with a compressed spring attached to the ceiling pushing on the
medium box.  Basically the ranking task is designed to elicit various
inappropriate conceptions.  It is somewhat helpful in getting students to
understand forces.  This ranking is long before any specific lessons
involving how buoyancy works, except for the idea that it is a force that is
present when an object is surrounded by a fluid.  MOP introduces all common
contact forces at once along with gravitational.  It takes a unified
approach to forces rather than isolating different forces in different
chapters.  I wish the standard texts took the same approach.

John M. Clement
Houston, TX

> It would go down.  You would quickly die and collapse, 
> thereby removing your weight from the scale.
>
> Paul
>
> On Jan 29, 2014, at 11:47 AM, Anthony Lapinski 
> <Anthony_Lapinski@pds.org> wrote:
>
> > Another related question. If you stand on a bathroom scale 
> and remove 
> > all the air in a room, what would happen to the reading?
>
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