Re: Newton's 2nd law Lab

[Rick Tarara <rbtarara@SPRYNET.COM>]

-----Original Message-----

> >                    With this group the pulley SIMPLY changes the
direction
> > of the force from vertical to horizontal.
>
> The *tape* changes direction when it is run over the pulley.  The only way
> to change the direction of a force applied by a fixed agency is by applying
> some other (noncolinear) force to add to it.  Do you think that this is
> beyond intro students' understanding? (I'm not sure I want to hear the
> answer to that one.)


Hear it!  The answer is almost certainly YES.

> So the students must wait, yet again, until some later course find out how
> they were swindled in their introductory course?  For a concept as
> fundamental as N2 is to introductory physics, I hope that this is not what
> others would advocate.

This is (it seems to me) a typical theorists point of view--'we _swindle_
students by not dealing with all the minute and often complicated details'.
Well I know of no intro text that deals with the details of how the pulley
'rotates' the vertical force of the falling weight into a horizontal force,
but there are generations of students who have worked with the modified
Atwood's machine 'as commonly presented'.  I wonder how swindled they are
feel!

This whole discussion does reaffirm a belief I've had since my college days
(long ago).  Theorists should be kept VERY far away from the introductory
courses.  ;-)

Rick