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MHT CET · Physics · Mechanical Properties of Fluids

A rectangular film of liquid is expanded from ( \(5 \mathrm{~cm} \times 4 \mathrm{~cm}\) ) to ( \(7 \mathrm{~cm} \times 8 \mathrm{~cm}\) ). If the work done is \(3 \times 10^{-4} \mathrm{~J}\), the surface tension of the liquid is (nearly)

  1. A \(0.4 \mathrm{~N} / \mathrm{m}\)
  2. B \(0.04 \mathrm{~N} / \mathrm{m}\)
  3. C 0.4 dyne/cm
  4. D \(4 \cdot 0 \mathrm{~N} / \mathrm{m}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(0.04 \mathrm{~N} / \mathrm{m}\)

Step-by-step Solution

Detailed explanation

\(A_1 = 5 \mathrm{~cm} \times 4 \mathrm{~cm} = 20 \mathrm{~cm}^2 = 20 \times 10^{-4} \mathrm{~m}^2\) \(A_2 = 7 \mathrm{~cm} \times 8 \mathrm{~cm} = 56 \mathrm{~cm}^2 = 56 \times 10^{-4} \mathrm{~m}^2\)
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