Surface Gravitation


For many problems, gravitation near the surface of the earth is applicable. This can be generalized to the gravitation on the surface of other bodies (assuming that the bodies have a definite surface), or to position above a body.	Sapience Home Site Map About Sapience Science Physics Mechanics Gravitation

For many problems, gravitation near the surface of the earth is applicable. This can be generalized to the gravitation on the surface of other bodies (assuming that the bodies have a definite surface), or to position above a body.

Content

All material bodies near the surface of the earth are subject to a force due to gravitation. This force is called the body's weight. It is directly proportional to the mass of the body:

W: weight (in Newtons)

m: mass (kg)

g: g (Free fall acceleration)

w = m*g

The free fall acceleration, g, often called the acceleration due to gravity, is the same for all bodies at a given location. It is different on different bodies in the solar system and it varies slightly from place to place on the earth's surface. These variations are produced by dynamic effects due to the earth's rotation, the height of the earth's surface, and irregularities in the surface and composition of the earth. They can be detected by instruments called gravimeters. A standard value for g has been assigned.

g₀ = 9.8 m*sec^-2

This value is usually simply called g, but it is here called here called g₀ to emphasize that it is a defined constant.

For most of history and even still in many contexts, weight is not distinguished from mass. This is reflected in the confusion that arises in the English system of units, in which the pound is sometimes considered a unit of force (as in mechanical engineering and most physics textbooks) and sometimes a unit of mass (as in chemistry and commerce).

The weight of a pound mass (lbm) where the free-fall acceleration is 1 standard g is 1 pound force (lbm)

Although the mass of a body is considered constant everywhere, its weight depends on the free fall accelaration at its particular location.

w = m * (g/g₀) * (1 lbf/lbm)


This depends heavily on other areas of physics including other areas of mechanics. It depends on particle mechanics, rigid body mechanics, nonrigid mechanics, and is connected to other aspects of gravitation. It is also connected to thermodynamics, electromagnetism, relativity, quantum mechanics, and the structure of matter. It has applications in chemistry, astronomy, earth science, and biology.	Sapience Home
Personal studies including the human body, psychology, and biography can be connected. Anthropology including social foundations, demography, physical anthropology, human ecology, human geography, and particular groups seems a bit less directly useful. Culture including material culture, conceptual culture, and behavioral culture will be useful in examining this subject. Institutions including families, education, economics, government, and religion will be useful. Sociology including social structure and change, communities, and peoples of the world will also be significant. History has some connections. Prehistory, antiquity, classical and medieval history, modern history, and the future will be connected as the site expands.

This depends heavily on other areas of physics including other areas of mechanics. It depends on particle mechanics, rigid body mechanics, nonrigid mechanics, and is connected to other aspects of gravitation. It is also connected to thermodynamics, electromagnetism, relativity, quantum mechanics, and the structure of matter. It has applications in chemistry, astronomy, earth science, and biology.

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Personal studies including the human body, psychology, and biography can be connected. Anthropology including social foundations, demography, physical anthropology, human ecology, human geography, and particular groups seems a bit less directly useful. Culture including material culture, conceptual culture, and behavioral culture will be useful in examining this subject. Institutions including families, education, economics, government, and religion will be useful. Sociology including social structure and change, communities, and peoples of the world will also be significant. History has some connections. Prehistory, antiquity, classical and medieval history, modern history, and the future will be connected as the site expands.