surface-tension-pulls-along-a-line - Surface Tension and Capillarity Step by Step

A surface-tension source and a contact length determine a line force. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

A contact line supplies the measured length

Start with one surface face. The line length and gamma source are visible before any force number is accepted.

\gamma=3\ \text{N/m}\qquad L=4\ \text{m}

Longer checked lines pull harder

Hold gamma and the surface count fixed. The force column changes only because the checked line length changes.

\begin{array}{c|c|c|c}n&\gamma&L&F\\1&3\ \text{N/m}&2\ \text{m}&6\ \text{N}\\1&3\ \text{N/m}&4\ \text{m}&12\ \text{N}\\1&3\ \text{N/m}&6\ \text{m}&18\ \text{N}\\\end{array}

A checked contact line sets the pull

The interface uses one surface-tension source and one visible line length before the force label is trusted.

F=\gamma L=3\ \text{N/m}\cdot4\ \text{m}=12\ \text{N}