A force field isa region in which an object will experience a non-contact force, such as a gravitational field. Any object with a mass will experience an attractive force if you put in the gravitational field of another object. Force fields are vectors.

The Earth's gravitational field is radial and the lines of the force meet at the centre of the Earth. The further away an object is from the Earth, the weaker the gravitational force. Close to the surface of the Earth, the field lines are (almost) uniform - parallel and equally spaced apart.

Point masses - objects which behave as if their mass is concentrated at the centre.

The Law of Gravitation is an inverse square law, meaning that if the masses increase then the force will decrease and if the distance doubles, the force will be one quarter of the original.

Gravitational Field Stregth is force per unit mass and its value depends on where you are in the field. g is a vector quantity and is always pointing towards the centre of mass whose field you are describing. It is often referred to as the acceleration due to gravity.

At some point between the Earth and the Moon, the Moon's gravity will be larger than that of the Earth. At some point the resultant field strength will be zero - this is known as the neutral point.

## Comments

No comments have yet been made