From a water tap, liquid comes out in form of cylinder. As water moves down, radius of that cylinder decreases. Consider, a very small element of height h and radius R (due to small height radius is a

Question

From a water tap, liquid comes out in form of cylinder. As water moves down, radius of that cylinder decreases. Consider, a very small element of height h and radius R (due to small height radius is assumed to be constant)

Question figure

This element is given in the diagram. An imaginary cross-section ABCD divides this element in two equal semi cylinders. S is surface tension of liquid. Now choose correct statement(s)

Question figure

TestHub · Accepted Answer

Only the curved liquid-air interface contributes to free surface area.

$A = 2 π R h$

$E = S A = 2 π R h S (D)$

The circular ends are imaginary sections within the same liquid, not free surfaces; A is false.

One principal curvature is 1/R and the axial curvature is zero.

$Δ P = S (\frac{1}{R} + 0) = \frac{S}{R}$

So the pressure difference in B is too large.

A lengthwise cut has two edges of length h. Each edge pulls with surface tension S per unit length.

$F = S h + S h = 2 S h (C)$

Physics - Fluid Question with Solution | TestHub

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