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Engineering ToolBox > Universal Gravitational Law
The gravitational attraction of two objects depends upon the mass of each object and the distance between them. This relationship is called the Gravitational Law and can be expressed as
F = kG m1 m2 / r2 (1)
where
F = gravitational force (N, lbf)
kG = universal gravitation constant = 6.67 10-11 (N m2/kg2)
m = mass of object (kg)
r = distance between objects (m)
The gravitational force (weight) on a person of 70 kg on the earth's surface (6.37 106 m from the earth's center) can be expressed as
F = 6.67 10-11 ( N m2/kg2) 5.98 1024 (kg) 70 (kg) / [6.37 106 (m)]2
= 688.1 (N)
5.98 1024 ( kg) is the mass of the earth.