**1. Introduction**

The theory of gravitational method based on Newton's law expressing the force of mutual attraction between two particles in term of their masses and separation.

This law states: (that two very small particles of mass (m1) and (m2) respectively, each with dimensions very small compared with the separation (r) of their centers of mass, will be attracted to one another with a force.

$$\mathbf{F} = \mathbf{G} \frac{m\_1 m\_2}{r^2} \tag{1}$$

G = Universal gravitational constant 667 x 10�<sup>8</sup> cm3 g �<sup>1</sup> s �<sup>2</sup> in cgs system 6.67 x 10�<sup>11</sup> (Nm<sup>2</sup> /Kg<sup>2</sup> ) in SI system If m1, m2 in gram and r (cm) The second law of motion expressed mathematically by the following. F = ma Where m = the mass a = acceleration,

r measured by (cm), M1, m2 measured in (gm), F measured by (dyne).
