### Category: Fluid Mechanics

Surface Tension of Water

## Introduction to surface tension of water

Surface tension of water is the property of water at rest by virtue of which its surface behaves like a stretched membrane and tries to occupy minimum possible surface area.

Mathematically, it is the force per unit length of an imaginary line drawn in the plane of water surface acting right angles to this line.

For any liquid,

Surface tension, T = F/l (where F is the force acing on the imaginary line of length l )

Value of surface tension of water in SI is 0.072 Nm-1 and in CGS is 72 dynes cm-1.

It means that it takes 0.072 Newton force to break the 1m long surface film of water .

This value of surface tension of water is higher than other liquids except the surface tension of mercury (0.425 Nm-1 ).  Surface Tension force acts in all directions parallel (i.e. tangential) to the water surface. Therefore, the free surface of water behaves like an elastic skin on a state of tension.