2nd year of post-compulsory secondary education
Gravitational fields
José Luis San Emeterio
 GRAVF 
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The principle of superposition

Newton's law of universal gravitation can be applied to two objects.

When we are dealing with systems with more than two objects, we must use the principle of superposition: The force exerted by one object on another is independent of the forces exerted by the other objects.

In sets like the solar system, where most of the mass belongs to only one of the heavenly bodies, the forces between the planets are in many cases negligible.

Click on Next to study a case in which this force should not be neglected. The visual shows a small asteroid moving between the sun and a big planet (Jupiter, for example).

Historical background
Freely falling bodies
Two theories of the universe
Kepler's laws
Conclusions
The force of gravity
Newton's law
The superposition of forces
Angular momentum and central force
Conclusions
Field intensity
The concept of field intensity
Variations according to position
Conclusions
Energy in the gravitational field
Gravitational potential energy
Equipotential surfaces and lines of force
Conclusions
Some consequences of the theory
Explanation of the tides
The movement of artificial satellites
Coherence of galaxies
Conclusions
Evaluation