Difference between revisions of "Gravity"
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Gravity
</dt>
1. Viewed from a frame of reference fixed in the earth, force imparted by
the earth to a mass which is at rest relative to the earth. Since the earth is
rotating, the force observed as gravity is the resultant of the force of gravitation
and the centrifugal
force arising from this rotation and the use of an earthbound rotating
frame of reference. It is directed normal to sea level and to its geopotential
surfaces. See virtual
gravity, geopotential
height, standard
gravity.
</dd>
The magnitude of the force of gravity at sea level decreases from the
poles, where the centrifugal force is zero, to the equator, where the
centrifugal force is a maximum but directed opposite to the force of
gravitation. This difference is accentuated by the shape of the earth, which
is nearly that of an oblate spheroid of revolution slightly depressed at the
poles. Also, because of the asymmetric distribution of the mass of the earth,
the force of gravity is not directed precisely toward the earth's center. The
magnitude of the force of gravity is usually called either gravity,
acceleration of gravity, or apparent gravity.
</dd>
2. = acceleration
of gravity.
</dd>
3. By extension, the attraction of any heavenly body for any mass; as
Martian gravity. [[/a>|/a>
]]
References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
