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The best driver in physics
Published in Jonathan Allday, Apollo in Perspective, 2019
When an object is released, it accelerates towards the ground as the planet pulls on it with the force of gravity, the force we call the weight of the object. The size of this force is determined by the mass of the object: the greater the mass, the heavier the weight: Weight = Mass × Gravitational field strength = Mass × g where g represents the gravitational field strength acting on the surface of the planet in Newtons per kilogram (N/kg). On Earth, this happens to be ∼9.8 N/kg. The strength of gravity is down to the mass (and radius) of the planet. On the Moon, the strength of gravity is ∼1.63 N/kg, that is, 1.63/9.81 = 0.166 or ∼1/6 the strength on Earth; hence we often read that the gravity on the Moon is 1/6 g.
Prospecting, exploration & site investigations
Published in Ratan Raj Tatiya, Surface and Underground Excavations, 2013
Gravity surveys: Normal earth gravity is 981 cm/sec2; any variation in this parameter is noted and after applying the correction due to latitude, elevation, topography and tidal change (i.e. change in gravity w.r.t. time). These surveys are of limited use in geotechnical evaluation of the orebody and the surrounding rock. The gravity meters measure the density at a particular point that is influenced by the density of materials all around the measured points. In figure 3.3(a) the presence of a dense body, which increases the force of gravity diverts the lines away from the vertical, as shown by the solid arrows. As distance from the dense body increases, the magnitude of gravitational field including its deviation from the vertical diminishes, and eventually disappears.
Introduction to geotechnical engineering
Published in Hsai-Yang Fang, John L. Daniels, Introductory Geotechnical Engineering, 2017
Hsai-Yang Fang, John L. Daniels
where FG force, m1, m2 = masses, r = distance between particles, and G = gravitational constant. The numerical value of the constant, G, depends on the units in which force, mass, and distance are expressed. Since the constant, G, in Equation (1.2) can be found from measurements in the laboratory, the mass of the earth may be computed. From measurements on freely falling bodies, we know that the earth attracts a 1 g mass at its surface with a force of about 980 dynes or 9.8 m/s2. The gravitational field is a condition in space setup by a mass to which any other mass will react.
A proposed new model for the prediction of latitude-dependent atmospheric pressures at altitude
Published in Science and Technology for the Built Environment, 2021
Because the earth is not a perfect sphere but rather an ellipsoid bulging at the equator, the acceleration due to gravity changes with latitude. The earth’s radius at the equator is greater than the radius at the poles and hence the gravitational field is slightly weaker. There are numerous correlations available, and with increased accuracy the complexity increases. The International Standard, ISO 2533:1975 (International Organization for Standardization 1975), suggests Lambert’s equation (Equation 24) to calculate a latitude-dependent value for the acceleration due to gravity. Consistent with this standard and the Department of Defense World Geodetic System 1984 (WGS84) (Department of Defense World Geodetic System 2000), the Greek letter is used to denote latitude and identify latitude-dependent sea-level values: where is the latitude-dependent acceleration due to gravity, m/s2.