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Re: Bulges




I don't think anyone mentioned a good article in The Physics Teacher.
Someone on another list kindly reminded me of it. Quoting from his msg:

[begin excerpt]

There is an article in the journal, "The Physics Teacher," (Vol.
32, Nov 1994, pages 492-495, available in most college and
university libraries) in which the gravitational force of an
obstetrician and the visible planets on a baby in a delivery room
are calculated. Reasonable assumptions are made about the masses
and distances of obstetrician and baby, and it is assumed the
planets in question are in opposition or inferior conjunction.
The force of Venus and Jupiter on the baby are each far greater
than the obstetrician, Saturn is roughly equal and Mars is
weaker. Strongest of all is the Moon, 1600 times greater than the
doctor.

It is pointed out, however, that the tidal forces experienced by
the baby due to its gravitational interaction with the
obstetrician are far greater than the tidal forces caused by any
of the planets. But how useful would it be to try to explain that
to non-technical people who never heard of the tidal force?

[end of excerpt]

Tidal effects are due to the gradient of the gravitational force. Every
object on earth, including you and I experience tidal effects from every
other object: earth, moon, sun, planets... Many textbook descriptions
confuse 'gravitational force' with 'tidal force', for which I prefer
'tidal effect'. The tidal effect is what is responsible for mechanical
stress and deformation of bodies.

-- Donald

......................................................................
Dr. Donald E. Simanek Office: 717-893-2079
Prof. of Physics Internet: dsimanek@eagle.lhup.edu
Lock Haven University, Lock Haven, PA. 17745 CIS: 73147,2166
Home page: http://www.lhup.edu/~dsimanek FAX: 717-893-2047
......................................................................