**13. Component of force**

The three basic principle directions of force are:

$$\begin{aligned} \mathbf{Fx} &\rightarrow & \mathbf{x} \\ \mathbf{Fy} &\rightarrow & \mathbf{y} \\ \mathbf{Fz} &\rightarrow & \mathbf{z} \end{aligned}$$

The equation of force lines are

$$\frac{\partial \mathbf{x}}{\partial \mathbf{x}} = \frac{\partial \mathbf{y}}{\mathbf{F} \mathbf{y}} = \frac{\partial \mathbf{Z}}{\mathbf{F} \mathbf{z}} \tag{44}$$

The force lines which pass a unit area (ds) vertically on the surface of the mass expressed as a Gravity Field Intensity

All points in the space outside the attractive mass in the potential gravity field characterized its subject to Laplace equation. The fact is the reason of ambiguity in gravity field.

*Gravitational Field - Concepts and Applications*

$$
\nabla^2 A = \frac{\partial^2 A}{\partial \mathbf{x}^2} + \frac{\partial^2 A}{\partial \mathbf{y}^2} + \frac{\partial^2 A}{\partial \mathbf{z}^2} = \mathbf{0} \tag{46}
$$

Where A is the potential field which is function of point position according to (x), (y), (z)
