In the 17th century Sir Isaac Newton discovered the Universal Law of Gravitation.

He observed the motion of planets along with Johannes Kepler`s planetary motion data.

Newton`s law of gravitation was formulated which describes the force of attraction between two masses.

The force of attraction between two masses depends on the size of the masses multiplied together and inversely proportional to the square of the distances apart.

The force of attraction is directly proportional on the product of the two masses.

The force of attraction is inversely proportional to the square of the distance from the centre of each mass

Combining both expressions we get this expression. Now we have to find the constant to give us the overall equation

Click on the PhET simulation to carry out a lab to determine the constant of the equation

The overall equation can be written as

G is called the Universal Gravitational constant and has a value of

Notice that the force of attraction that small mass m has on large mass M is exactly the same as the size of the force of attraction large mass M has on small mass m.

Calculate the size of the gravitational force between two human beings.