Sometimes it has to do with orientation . A diagonal line is more dynamic than a horizontal or verticl line. Sometimes motion depends on the character of the element itself. A straight line may be less dynamic than a zigzag or a curving line. A blended area may appear to flow.
Depth is another magic effect.
Illusion and magic are two threads of the same cloth. Sometimes the illusion of depth has to do with orientation . If you want a chair or person to appear further away, you can place them higher on the picture plane. Sometimes the illusion of depth depends on the character of the element itself. A warm color can appear to project and cool color can appear to recede, other things being equal.