2016 Phase II Mechanical Properties of FluidsSurface tension – surface energy Easy Question 27 of 34 in Mechanical Properties of Fluids

A rectangular film of liquid is extended from (4 cm × 2 cm) to (5 cm × 4 cm). If the work done is $3 \times 10^{-4}$ J, the value of the surface tension of the liquid is:

A 0.2 $Nm^{-1}$
B 8.0 $Nm^{-1}$
C 0.250 $Nm^{-1}$
D 0.125 $Nm^{-1}$

The answer is D.

Solution

Liquid film has two free surfaces.

$W = T(2\Delta A)$ (the film has two surfaces); $\Delta A = 20 - 8 = 12\ cm^2$
$T = \frac{W}{2\Delta A} = \frac{3\times10^{-4}}{2\times12\times10^{-4}} = 0.125\ Nm^{-1}$

Concept film-surface-tension-work

Mechanical Properties of Fluids in past papers

34 questions from this chapter have appeared across 14 exam years.