Re: [Phys-l] Equations

["John Clement" <clement@hal-pc.org>]

This reasoning exposes one of the problems that students have with
gravitation.  F_g = m g is not understood when g is formulated as 9.81
m/s^2.  But it is much more understandable when g = 9.81 N/kg.  I think most
of the PER researchers are probably in agreement on this point.  When g is
formulated as an acceleration the students wonder why there is a
gravitational force when the object is not acceleration.

John M. Clement
Houston, TX


> John Denker wrote, in part:
> "Saying
>          F causes ma                             (1)
> is just as true (or just as false) as saying
>          ma causes F.                            (2)"
>
> I continue to disagree.  Forces can exist in the absence of
> acceleration, but acceleration cannot exist in the absence of forces.
>
> A system can be in equilibrium while being subjected to two or more
> forces.  It is certainly perverse to suggest that these forces are
> caused by acceleration.
>
> Daniel Crowe
> Oklahoma School of Science and Mathematics
> Ardmore Regional Center
> dcrowe@sotc.org
> _______________________________________________