[Phys-L] Re: PHYS-L Digest - 21 Oct 2005 to 22 Oct 2005 (#2005-371)

[jsteinert at AUBURNSCHL.EDU (Jeff Steinert)]

Forum for Physics Educators <PHYS-L@list1.ucc.nau.edu> on Saturday,
October 22, 2005 at 5:00 AM -0500 wrote:
> The problem below is
> correct except that the force is acting on Block 2 and NOT on Block 1
> I wanted to know why the the net force equation seem to imply that
> there was a value of friction between the blocks that kept Block 2
> from accelerating.

There IS a value of Fpull for which Block 2 does not accelerate.  Block 2
is, however, in motion when it occurs.  It is a kinetic friction force
between Blocks 1 and 2 that provides the balancing force.  As long as the
friction force between the blocks remains static friction, the two blocks
accelerate as one.  I'm sure someone else will provide the details.  My
almost two-year-old son is now waking from his nap and calls me away.

Yours,

Jeff Steinert                   School:  207-783-8528
Physics Instructor              jsteinert@auburnschl.edu
Edward Little High School
2 Auburn Heights                Home:  207-725-5875
Auburn, ME 04210                tristan2@suscom-maine.net

"It is a profound and necessary truth that the deep things in science are
not found because they are useful; they are found because it was possible
to find them."
                                                                J. Robert Oppenheimer