JEE PYQ: Mechanical Properties Of Fluids Question 12
Question 12 - 2020 (03 Sep 2020 Shift 1)
When a long glass capillary tube of radius 0.015 cm is dipped in a liquid, the liquid rises to a height of 15 cm within it. If the contact angle between the liquid and glass is close to 0$^\circ$, the surface tension of the liquid, in milliNewton m$^{-1}$, is [$\rho_{\text{(liquid)}} = 900$ kgm$^{-3}$, $g = 10$ ms$^{-2}$] (Give answer in closest integer) ______
Show Answer
Answer: 101
Solution
Given: Radius of capillary tube, $r = 0.015$ cm $= 15 \times 10^{-5}$ m $h = 15$ cm $= 15 \times 10^{-2}$ m Using $h = \frac{2T\cos\theta}{\rho g r}$ [$\cos\theta = \cos 0^\circ = 1$] Surface tension, $T = \frac{r h \rho g}{2} = \frac{15 \times 10^{-5} \times 15 \times 10^{-2} \times 900 \times 10}{2} = 101$ milli newton m$^{-1}$
BETA
