Question

When a tube of length $10\text{cm}$ is dipped in water, the water rises up to $6\text{cm}$. If the entire arrangement is put in a freely falling elevator, the length of water column in the capillary tube will be

• A. $2\text{cm}$
• B. $6\text{cm}$
• C. $10\text{cm}$
• D. $4\text{cm}$

Answer 1

The correct option is C $10\text{cm}$

The height of rise of water in the capillary is given by
$h=\frac{2\sigma \cos \theta }{\rho gr}$

In the free-falling elevator, the relative acceleration due to gravity becomes zero and the height of the water inside the capillary becomes infinity. So the water will fill the entire tube, and the tube's length is $10\text{cm}$.