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Physics · PYQ NEET UG 2016(2)
हिन्दीA rectangular film of liquid is extended from \( (4\text{ cm} \times 2\text{ cm}) \) to \( (5\text{ cm} \times 4\text{ cm}) \). If the work done is \( 3 \times 10^{-4}\text{ J} \), the value of the surface tension of the liquid is
Correct answer · Option 3
\( 0.125\text{ Nm}^{-1} \)
Explanation
Initial area \( A_1 = 2 \times (4 \times 2 \times 10^{-4}) = 16 \times 10^{-4}\text{ m}^2 \). Final area \( A_2 = 2 \times (5 \times 4 \times 10^{-4}) = 40 \times 10^{-4}\text{ m}^2 \). \( W = T \Delta A \implies 3 \times 10^{-4} = T (24 \times 10^{-4}) \implies T = \frac{3}{24} = 0.125\text{ Nm}^{-1} \).
