Re: Newton's 2nd law Lab

[Rick Tarara <rtarara@SAINTMARYS.EDU>]

Again you complicate this beyond the Introductory level--especially
non-physics majors.  With this group the pulley SIMPLY changes the direction
of the force from vertical to horizontal.  We NEVER complicate things by
determining the 3-dimensional force vectors that accomplish this.  Your
comments and concerns are appropriate to a 2nd course in mechanics, NOT the
intro physics courses for which these labs are designed.

Rick


-----Original Message-----
From: David Bowman <dbowman@TIGER.GEORGETOWNCOLLEGE.EDU>

> I don't care about the negligible tangential friction forces on the
> string going over the pulley.  I care about the much stronger forces
> acting radially away from the pulley's center on the string.  The
> resultant of these forces has a horizontal component which is sufficient
> to accelerate the cart horizontally (via its imposition of a horizontal
> tension in the horizontal part of the tape) and has a vertical component
> to provide the vertical tension in the vertical length of tape which
> tends to retard the acceleration of the falling mass.



etc.