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Law of Universal Gravitation

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-80

2025-11-04

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Gravitation is the name given to the mutual attraction between different bodies of matter. The matter considered may be two books lying on a table, or two stars separated by millions of miles. The attraction is universal, and the Law of Universal Gravitation may be stated as follows:

 Every particle of matter in the universe attracts every other particle with a force that varies directly as the product of the masses of the particles and inversely as the square of the distance between them. This leads to the formula which is applicable to all mutual attractions, namely,

in which a is the unit of attraction; i.e.; the attraction between two units of mass at a unit's distance.

For comparing two attractions of the same kind we may write the proportion

The momenta given by mutual attraction to the two bodies between which the attraction acts, are equal. A man standing in a rowboat and pulling on a rope that is fast to a sloop moves the boat faster than the sloop, but only because its mass is much less. The momentum imparted to the sloop is equal to that given to the rowboat.