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Re: Weight

At 5:15 PM on 4/9/97, <RAUBERJ@mg.sdstate.edu> wrote:


David wrote and Marlow cheered


BTW, since gravitational forces (locally) are not "real" but are artifacts
of
the use of a noninertial frame used to describe the physics, I prefer
*not*
to define the concept of "weight" as (the magnitude of) the gravitational
force on an object. Such a definition makes an object's weight depend on
the
coordinate system of the observer. I prefer to define weight as what
others
define as "apparent weight" which is simply the magnitude of the
*non*gravitational force of support on a body which prevents a free fall
state (or equivalently, which deflects the motion from a free fall state).
This definition of weight is independent of the frame of the observer and
agrees with our usual sensations of weight.

I too define weight in this fashion, although for simpler reasons than
talking about non-inertial frames, and free-fall frames etc.

Simply put, if you define weight to be the gravitational force acting on an
object; how do you explain why we say astronoughts are weigtless while
orbiting the earth, since they still have a gravitational force acting on
them.

Therefore defining weight as the magnitude of the non-gravitational force
present balancing the gravitational force on the scale used, relieves one
from the above conundrum and allows one to consistantly understand the term
weightless up on the space-shuttle

Joel

A good point, but since this definition depends on the vertical component
of acceleration, maybe we should dispense with the use of the word "weight"
from our explanations entirely. I would hate to tell a student swinging a
bucket in a vertical circle that the "weight" of the bucket was varying in
magnitude and alternately up then down. I'd rather talk about the tension
in the rope.

Likewise rather than calling the normal force holding you up your "weight",
maybe we should just call it the normal force.

Chip