Newton's Law of Universal Gravitation

In Words
Every body attracts every other body in the universe with a force that is directly proportional to the product of the masses of the two bodies and inversely proportional to the square of the distance between their centres.

In simple words, this means that any object that has mass, automatically attracts another object that has mass!

Study this diagram.



These two masses are attracting each other with a force called a Gravitational Force. The distance between them, from center to center, is called r.

This force can be calculated from this equation :

G is called the Universal Gravitational Constant.
And it is ALWAYS
6,67 x 10-11N.m2kg-2.

Chill, it's on the data sheet!

Some of the constants from the Data Sheet.


Calculate the Gravitational Force of Attraction between these two masses.





The diagram can then be drawn like this, showing TWO forces.
Althought only ONE force was calculated, there are actually TWO forces, one per mass. This is because of Newton's Third Law :


The two forces are the same size even though the masses are different.






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