Q119 / 150 · MHT CET 2020 (14 Oct Shift 1) · Physics

One thousand small water drops of equal radii combine to form a big drop. The ratio of final surface energy to the total initial surface energy is

  • A
    1:1000
  • B
    1:1
  • Correct answer
    C
    $1: 10$
  • D
    $1: 100$

Solution

$U_{1}=1000 \times 4 \pi r_{1}^{2} \times T$ $\frac{r_{2}}{r_{1}}=(1000)^{1 / 3}=10$ $U_{2}=4 \pi r_{2}^{2} T$ $\frac{U_{2}}{U_{1}}=\frac{4 \pi r_{2}^{2} T}{1000 \times 4 \pi r_{1}^{2} \times T}=\frac{100}{1000}=\frac{1}{10}$

Hence, the correct answer is option: 'C'.

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