Re: Internal or external?

[Joel Rauber <Joel_Rauber@SDSTATE.EDU>]

> Ludwik wrote
> > Should we also insist on the "earth
> > acting on the rock with the force W"? Would the "F acting
> > on Q" irritate you?
>
> What I would much rather have students say and write and think is "W
> is the force exerted by the earth on the rock"
> See, for example, Lillian McDermott's Tutorials in Introductory
> Physics.
This would provide an excellent segue to the weight/weightless discussion,
i.e. is weight what is measured on the scale or is it Mg?  I.e. is weight
synonomous with the "force of gravity" the force exerted by the earth on the
rock in the above example?

Sorry for bringing this up again.

Joel