Re: [Phys-l] g...

["Anthony Lapinski" <Anthony_Lapinski@pds.org>]

There's confusion with this in many places (esp. "g" forces). I tell my
students that "g" is an acceleration, not a force. When I ask for free
body diagrams, they usually say one of the forces is "gravity" downward.
Well, it's technically "weight" downward. Forces always involve two
objects, so the Earth's gravity is not a force.

The more difficult concept is teaching students that the shuttle
astronauts are not truly weightless (i.e., g ? 0 up there in orbit)...

Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu> writes:
> I have a problem with g.  Despite my best efforts many of my students
> still want to say that g is a force.  I can see where the whole thing
> would be confusing for them.  Our first experience with g is to call it
> the acceleration of gravity on Earth.  I stress over and over that it is
> not "gravity", it is not "the force of gravity", it is the acceleration
> that objects undergo as they fall to the Earth.  However, bout the time I
> think that I have that idea pumped into their heads we start using g to
> find weights w=mg.  Now the object is not accelerating at all so what's
> g?  I usually only address the idea that g is now being used as a
> constant that represents the strength of the gravitational field if one
> of my students brings it up, and that's not very often.  Maybe that's a
> mistake.  Now g is appearing once again in Newton's Universal Law of
> Gravity this time twice... Fg = G m1 m2 / d^2   I asked my students to
> describe what g was on a quiz yesterday and got back answers that
>  were all over the map.  Any advice?
>
> Cliff Parker
> Never express yourself more clearly than you can think. 
> - Niels Bohr
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