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JEE Main202120 Jul 2021Evening ShiftPhysicsMechanical Properties of FluidsActual

Two small drops of mercury each of radius R coalesce to form a single large drop. The ratio of total surface energy before and after the change is

Options

  1. A2 1 3 : 1
  2. B1 : 2 1 3
  3. C  2 :   1
  4. D1 :   2

Correct answer

A. 2 1 3 : 1

Step-by-step solution

4 3 π R 3 + 4 3 π R 3 = 4 3 π R ' 3 R ' = 2 1 3 R     … i A i = 2 4 π R 2 A f = 4 π R ' 2 U i U f = A i A f = 2 R 2 2 2 3 R 2 = 2 1 3

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