A drop of liquid of radius R = 10 - 2 m having surface tension S = 0.1 4 π N m - 1 divides itself into…

A drop of liquid of radius R=10-2m having surface tension S=0.14πNm-1 divides itself into K identical drops. In the process the total change in the surface energy ΔU=10-3J . If K=10α then the value of α is

Solution

By mass conservation, ρ .43 πR3=ρ.K.43πr3

    R=K13 r

     ΔU=T ΔA=T K. 4πr2-4πR2

=T K. 4πR2K-23-4πR2

ΔU=4πR2T K13-1

Putting the value’s      10-3=10-14π×4π×10-4K13-1

100=K13-1

    K13 100=102

Given that  K=10α       10α3=102

   α3=2

     α=6

Asked in: JEE Advanced 2017 (Paper 1)

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