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JEE Advanced 2017Paper 1
Exam
JEE Advanced
Year
2017
Paper
Paper 1
Subject
Physics
Chapter
Mechanical Properties of Fluids

JEE Advanced 2017 · Paper 1 · Physics · Mechanical Properties of Fluids

A drop of liquid of radius R = 10 ^ - 2 m having surface tension S...

A drop of liquid of radius R=10−2mR = {10}^{- 2}m having surface tension S=0.14πNm−1S = \dfrac{0.1}{4\pi}N{m}^{- 1} divides itself into K identical drops. In the process the total change in the surface energy \DeltaU=10−3J\DeltaU = {10}^{- 3}J . If K=10αK = {10}^{\alpha} then the value of α\alpha is

Correct answer

0

Step-by-step solution

By mass conservation, ρ . \dfrac{4}{3}π{R}^{3} = ρ . K . \dfrac{4}{3}π{r}^{3}

→R=K13r\to R = {K}^{\dfrac{1}{3}}r

∴ ΔU = TΔA = T\left(K . 4π{r}^{2} - 4π{R}^{2}\right)

= T\left(K . 4π{R}^{2}{K}^{- \dfrac{2}{3}} - 4π{R}^{2}\right)

ΔU = 4π{R}^{2}T\left[{K}^{\dfrac{1}{3}} - 1\right]

Putting the value’s \to {10}^{- 3} = \dfrac{{10}^{- 1}}{4π} × 4π × {10}^{- 4}\left[{K}^{\dfrac{1}{3}} - 1\right]

100=K13−1100 = {K}^{\dfrac{1}{3}} - 1

\to {K}^{\dfrac{1}{3}} ≅ 100 = {10}^{2}

Given that K = {10}^{α} \to ∴ {10}^{\dfrac{α}{3}} = {10}^{2}

\to \dfrac{α}{3} = 2

\to α = 6

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