Re: [Phys-L] inertia and the tablecloth demo

[Bernard Cleyet <bernard@cleyet.org>]

> On 2016, Aug 19, , at 20:46, Anthony Lapinski <alapinski@pds.org> wrote:
>
> I first teach about true weight (mg -- downward) and apparent weight (scale
> reading, normal force -- upward). The MC answers are constructed so there
> is no ambiguity (earth on book, book on earth, table on book, book on
> table). I'm sure others teach weight differently as this discussion has
> come up before on this listserv.


Thank you.  this totally mystified:  


On 2016, Aug 19, , at 19:12, Anthony Lapinski <alapinski@pds.org> wrote:

It doesn't seem like a poor question. It's a MC question with four choices.
As Richard responded, weight is Earth pulling down on the book (I teach
this during the second law), so the reaction is the book pulling up on the
Earth. One of many action-reaction cases. A on B, B on A etc.


As an added experiment use an optical lever to show the table is depressed when the book is placed.  Or a 25#” weight" if necessary.   


bc should learn to read carefully?