Q. When a glass capillary tube of radius 0.015 cm is dipped in water, the water rises to height of 15 cm within it. Assuming contact angle between water and glass to be $0{^\circ}$, the surface tension of water is $\lbrack\rho_{water\ } = 1000\ kg\ m^{- 3},\ g = 9.81\ {ms}^{- 2}\rbrack$
A) $0.11{Nm}^{- 1}$
B) $0.7{Nm}^{- 1}$
C) $0.072\ {Nm}^{- 1}$
D) None of these
Explanation
(a) $2\pi r \times T\ cos\theta = \pi r^{2}h\rho g$
$\Longrightarrow \ \ T = \frac{rh\rho g}{2} = 0.11{Nm}^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.