Universal Gravitational Law

Gravitational attraction of two objects depends upon mass of objects and the distance between them

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 = k_G m₁ m₂ / r²         (1)

where

F = gravitational force (N, lb_f)

k_G = universal gravitation constant = 6.67 10^-11 (Nm²/kg²)

m = mass of object (kg)

r = distance between objects (m)

Example - The gravitational force on a person on earth's surface

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 Nm²/kg²) (5.98 10²⁴ kg) (70 kg) / (6.37 10⁶ m)²

    = 688.1 (N)

• 5.98 10²⁴ (kg) = mass of earth

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