Question

If the force required to pull out a glass plate of length $9.8cm$ and thickness $2mm$ from a liquid is $0.6gm-wt.$ The surface tension of water is $N{m}^{-1}$:

• A. $2.94\times {10}^{-3}$
• B. $29.4\times {10}^3$
• C. $29.4\times {10}^{-2}$
• D. $29.4\times {10}^{-3}$

Answer 1

The correct option is D $29.4\times {10}^{-3}$

Force = surface tension X 2(length + thickness)
$Surfacetension=\frac{0.6\times 9.8\times {10}^{-3}}{2(9.8+0.2)\times {10}^{-2}}$

$=29.4\times {10}^{-3}N/m$

Option D is correct.