What forces are NOT affecting the rise or fall of liquid in a small-diameter capillary tube?

In the context of liquid behavior in a small-diameter capillary tube, it's essential to understand the role of various forces at play. Adhesive forces are the attractive forces between the liquid molecules and the molecules of the tube's surface, which contribute to the rise of the liquid due to capillarity. Cohesive forces are the intermolecular forces within the liquid itself, which help maintain the liquid's integrity and influence its movement. Surface tension arises from the cohesive forces at the liquid's surface and affects how the liquid interacts with its environment, also contributing to its ability to rise or fall in the tube.

Fluid viscosity, while it characterizes a liquid's resistance to flow and plays a crucial role in the movement of liquids generally, does not directly influence the rise or fall of liquid in a capillary tube. Instead, viscosity governs the flow rate and dynamics of the liquid once it is in motion. Therefore, while viscosity is important in broader fluid dynamics, it does not affect the capillary action specifically, which relies primarily on adhesive forces, cohesive forces, and surface tension to determine how high or low a liquid will rise or fall in a small-diameter tube.