Universal Gravitational Law

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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 = 6.668 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 = (6.668 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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Related Topics

• Dynamics - Dynamics Motion - velocity and acceleration
• Mechanics - Kinematics, forces, vectors, motion, momentum, energy and the dynamics of objects

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