Q 11-09-024NEETJEE MainMedium
Water (surface tension $0.07$ N m$^{-1}$, contact angle $0^\circ$) rises in a glass capillary of radius $0.5$ mm. The height of rise is ($g = 10$ m s$^{-2}$)
Answer: (B) $2.8$ cm
Concept. Capillary rise: $h = \dfrac{2T\cos\theta}{\rho gr}$.
Step 1. Substitute.
$$h = \frac{2 \times 0.07}{1000 \times 10 \times 5 \times 10^{-4}} = 0.028\ \text{m} = 2.8\ \text{cm}$$
Answer. $2.8$ cm (Option B).
Solution by Sreeraj P, M.Sc Physics