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Name: Lorna
Status: student
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Question:
I know that the density of the materials on Earth affect the gravitational field intensity. What are some other factors that affect the local intensity of gravity? Latitude? Altitude? others?


Replies:
Lorna,

Altitude does affect the local gravitational acceleration. When two objects move away from each other, the gravitational force they exert on each other weakens. As a result, each experiences a smaller acceleration due to gravity. A high altitude location is further away from Earth than is a low altitude location. I am told that gravitational acceleration at the top of a tall mountain can be as 0.2m/s^2 less that at the bottom of the mountain. I am sure there are other effects, but this one is the easiest to actually measure.

Ken Mellendorf


Lorna,

In the simplest terms, the distance between two bodies of masses is exponentially, inversely proportional to the gravitational field intensity.

In other, words, the further the distance between two bodies of masses, in this case by altitude from the earth's center of mass, the weaker the gravitational force or intensity between the two bodies.

-Alex Viray


My MS work included a gravity survey in Utah and I assure you that elevation, latitude, time of day, positions of the sun and moon, nearby topography such as hills and valleys, the type of rock you are standing on, and even the time of year all affect the value of gravity you measure. That is if you are sitting still on land. If you are measuring gravity on the ocean from a moving ship here are several other effects that come into play.

Space and time are limited so before I get too heavily into the subject, let me recommend that you look up "gravity surveying" and/or "gravity surveying corrections" on Google. You will get more information than you probably want. Also if you can find a book entitled "Geophysical Prospecting" by Milton Dobrin, there is a good treatment of gravity in there, too.

R. W. "Bob" Avakian
Instructor
Oklahoma State Univ. Inst. of Technology



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