NEWTON'S LAW OF UNIVERSAL GRAVITATION

(Be sure to read Section 2.5 in your book.) According to Newton's Law of Universal Gravitation, the force of gravity between any two bodies is directly proportional to the masses, and inversely proportional to the square of the distance between them (separation):

g = (GM 1 m 2 )/D 2

Where M 1 and m 2 are the masses of the two objects and the separation (D) is measured between the centers of the two masses.

In other words, if the mass of the system increases (or decreases), the force of gravity between the two bodies changes in direct proportion. If you double the mass, you double the force. On the other hand, if the separation between the two bodies changes, the change in force is proportional to the inverse of the change in separation squared. In other words, take the change in relative distance, square it, then divide the original force value by this. If the separation doubles (2), then the inverse square is 1/2*2 or 1/4. Thus the value for the force would go down to one fourth the original value. Try plugging in some values to see what happens. (If the mass decreases by 1/2, use .5 and so on.):

Enter Mass Change:
("2" means double the mass and so on.)
Enter Separation Change:
("2" means double the separation and so on.)

The resulting gravitational force would be times the initial value.
If your browser isn't JAVASCRIPT capable, you will not see the form above.
Return .