One in the x direction and the other in the y direction.

Assuming one dimensional flow in the x direction it follows that:

Here the center of mass will only be found in the x direction.

Thus the amplitude of the differential (tidal) change in lengths between nearby points along the x direction.

That is, there is the most variance in the "x" direction.

So that, if u1 was the extension in the x direction, we would write the strain as δu1/δx.

The x direction might be chosen to point down the ramp in an inclined plane problem, for example.

The ladder is moving at a velocity of in the positive x direction, therefore .

The wave equation dictates the motion of the wave in the x direction.

In the x direction and in the y direction .