What is the SI unit of surface tension? 

Surface tension is a physical property of liquids that results from the cohesive forces between liquid molecules. At the surface of a liquid, the molecules experience an inward force due to the attraction from the molecules beneath them, leading to the formation of a surface that resists external forces.

Mathematically, surface tension is defined as the force per unit length exerted along the surface of a liquid. The formula for surface tension is:

Surface Tension = Force / Length

Where:

• Force is the force applied along the surface, measured in Newtons (N).
• Length is the length along the surface where the force is applied, measured in meters (m).

Therefore, the unit of surface tension is Newton per meter (N/m), or equivalently, Newton meter raised to the power of minus one (N·m^-1).