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Re: [Phys-l] NYT article: Centrifugal force



On 07/02/2009 11:29 AM, bettyjspace-1@yahoo.com wrote:
The following excerpt is taken from Tuesday's NYT, and the quote is
attributed to the associate director of the division of ocean and
climate physics at the Lamont-Doherty Earth Observatory of Columbia
University. Any thoughts with respect to the use here of the
centrifugal force?

The article looks good to me. The physics is correct, and is well
explained. For the next level of detail, see
http://www.av8n.com/physics/weight.htm

Through no fault of Dr. Gordon, I'm not happy with the terminology
of "gravity" versus "observed gravity". IMHO the "observed gravity"
should be called "the" gravity. But alas this is not (yet) a
constructive suggestion, because it leaves the community without
a good name for the other contribution to the (observed) gravity,
namely the part we would calculate from Newton's law of universal
gravitation, ignoring the centrifugal contribution. I've been
scratching my head for years, trying to find a good name for this
contribution, without finding anything I'm completely happy with.

Half-baked suggestion of the day: How about the "jet set" gravity,
i.e. the gravity that you would measure in an airplane flying east
to west just fast enough to cancel the rotation of the earth. e.g.
an airplane that took off at noon and flew west just fast enough
to keep the sun directly overhead for the duration of the measurement.
-------> Does anybody have a better suggestion??????


The Earth’s Paunch By C. CLAIBORNE RAY Q. I know the earth bulges at
the equator. Does this include the oceans?

A. There is an oceanic bulge, said Arnold L. Gordon, associate
director of the division of ocean and climate physics at the
Lamont-Doherty Earth Observatory of Columbia University.

“As the earth spins, a centrifugal force is directed outward, away
from the axis of rotation,” Dr. Gordon said. “This force is strongest
for a particle at the equator that has a longer path to follow around
the earth’s axis each day, despite its greater distance from the
earth’s axis.” Meanwhile, he said, gravity, as induced by the earth’s
mass, is also acting on each particle. The forces combine to produce
what is called the observed gravity, which does not point to the
earth’s center, but is off center.