Physics - Fluid Question with Solution | TestHub

The upward force due to surface tension is given by $F=T\times C\times \cos \theta$, where $C$ is the inner circumference of the capillary tube and $\theta$ is the angle of contact.

For water, the angle of contact is $\theta =0^{\circ }$, so $\cos \theta =1$.

Given $F=98\text{ dyne}=98\times 10^{-5}\text{ N}$ and $T=7\times 10^{-2}{\text{ N m}}^{-1}$.

Substituting the values, we get:

$98\times 10^{-5}=7\times 10^{-2}\times C$

$C=\frac{98\times 10^{-5}}{7\times 10^{-2}}\text{ m}$

$C=14\times 10^{-3}\text{ m}$

Converting to centimeters:

$C=14\times 10^{-3}\times 10^2\text{ cm}=1.4\text{ cm}$

Answer: 1.4 cm