# Shared Flashcard Set

## Details

Geophysics Test 1
Gravity in Geophysics
18
Geology
10/11/2015

Term
 Kepler's Law 1
Definition
 The orbit of each planet is an ellipse with the sun at one focus.
Term
 Kepler's law 2
Definition
 the line between a planet and the sun sweeps out equal areas in equal time.
Term
 Keplers Law 3
Definition
 the ratio of the squares of the periods to the cubes of their average distances to the sun is the same for everyone of the planets.
Term
 Moments of Inertia
Definition
 can deduce information on the distribution of mass within the earth. Done by calculating and comparing the moments of ineritia about different axes throug the earth. Directly related to the kinetic energy due to it's rotational velocity.    KE=1/2mv^2     v^2=w^2(r^2) KE=1/2m(w^2r^2) KE=1/2w^2(I)    I=mr^2
Term
 Gal
Definition
 1 gal=1cm/s^2 1 mgal=.001cm/s^2
Term
 Precession
Definition
 the force of the sun applies a torque on the equitorial bulge which causes the axis of rotation to move in a clockwise motion. Changes seasons every 27,000 years.
Term
 Centrifugal forces
Definition
 outward forces due to earths rotation. Max at equator, min at poles.
Term
 Spring Tide
Definition
 when sun and moon are inline with the earth. Extra large tides occur since moon and sun gravity working together
Term
 Neap Tide
Definition
 when sun and moon are perpendicular to the earth. will cause weaker tides because sun and moon gravity work against each other
Term
 Tidal Drag
Definition
 Earth spinning faster than the moon, so tidal bulge is in front of the direct line from earth to moon. Moon's gravitational force pulls back the bulge and causes slowing of the earth. This also causes the moon to speed up which contributes to lunar regression. Overall equilibrium is the moon orbiting at the same velocity the earth is spinning.
Term
 Geoid
Definition
 Equipotential Surface of the real earth as it exists. Equilibrium surface that water would obtain on the surface of the present earth.
Term
 Spheroid
Definition
 Equipotential surface that would be obtained over an ideal axially symmetric earth as described by international gravity formula.
Term
 Milankovitch Cycles
Definition
 Eccentricity: every 100,000 years Axial Tilt: 2 degree change every 40,000 years Precession: every 27,000 years
Term
 Roche Limit
Definition
 Orbital distance to which a body will begin to break up under the action of tidal forces. When gravitational and centripetal forces due to the parent planet are equal to the gravitational forces between different parts of the body itself.
Term
 Tides developing on opposite side of the moon
Definition
 due to centrifugal forces from the rotation of the earth
Term
 Satellite Orbit
Definition
 determined by the balance of gravitational and centrifugal forces.
Term
 precession of the orbit of the satellite
Definition
 centrifugal force constant, variation in the gravity field causes the orbit to precess.
Term
 Ellipticities of the Earth
Definition
 Homogeneous hydrostatic, satellite, hydrostatic, dynamical, spherical
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