AIIMS 2019 Physics Energy and Surface Tension MCQ Question
A mercury drop of radius 1 cm is sprayed into 10⁶ drops of equal size. The energy expressed in joule is (surface tension of mercury is 460×10⁻³ N/m)
0.057
5.7
5.7×10⁻⁴
5.7×10⁻⁶
Correct Answer
Detailed Explanation
When a mercury drop of radius 1 cm is divided into smaller drops, the radius of each smaller drop becomes r = \frac{1 \, \text{cm}}{10^6^{1/3}} \approx 0.001 \, \text{cm}. The energy associated with the surface tension can be calculated using the formula , where is the change in surface area and is the surface tension. The initial surface area of the larger drop is and the total surface area of the smaller drops is . Calculating the energy change yields approximately , making option A correct. The other options are incorrect as they either underestimate or overestimate the energy change based on incorrect calculations of the surface area or the surface tension.
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