The gravitation force is exerted by the planet Earth ,

where  is the mass of Earth.

            is its radius.

           is the gravitational constant.

           distance from the center of the earth.

Definition of continuity :

A function  is continuous at , if  then it should satisfy three conditions :

(1)  is defined.

(2)  exists.

(3) .

Condition (1):

 is defined.

If  then the function is .

Substitute  in the above function.

.

Condition (2):

 exists.

Left hand limit :

Right hand limit :

Left hand limit and right hand limit are equal, limit exist.

.

Condition (3):

.

 and .

.

The three conditions of continuity are satisfied, hence the function is continuous.

Therefore, the function  is continuous at .

The function  is continuous function of .