Question

2. c) A capillary tube with an inside radius of 638 nm can support a 100 mm column of liquid that has a density of 820 kgm3. The observed contact angle is 12.5°. Find the surface tension of the liquid for h= 20 cm.

Answer 1

As we know,

$$h=\frac{2\sigma\cos\theta}{\rho gr},\\\space\\ \sigma=\frac{\rho grh}{2\cos\theta}=5.25·10^{-4}\text{ N/m}.$$