Gravitational fields

What do we already know about gravitational fields?

We know that the earth's gravitational field strength is 9.81Nkg ¯¹ .
When you throw a ball into the air and it returns to you because of the earth's gravitational force. The force of gravity on the ball pulls it back to earth.

The force of attraction between the ball and the earth is an example of gravitational attraction. This attraction exists between any two masses but we don't notice it since it's force is too weak. The time we notice it, it's when one of the masses is very large.

The mass of an object creates a force field around itself. Any other mass placed in the field is attracted towards the object. The second mass also has a force field around itself and this pulls on the first object with an equal force in the opposite direction. The force field round a mass is called a gravitational field.

The strength of a gravitational field(g) is the force(F) per unit mass(m)
= g=F/m : Nkg ¯¹