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MHT CET 2025 (25 Apr, Shift 2) · Surface Energy & Work Done

Surface Energy & Work Done question from MHT CET 2025 (25 Apr, Shift 2)

Q10MHT CET 2025 · 25 APR · SHIFT 2Medium

Surface Energy & Work Done

The amount of work done in blowing a soap bubble such that its diameter increases from 'd' to ' DD ' is ( T=T = surface tension of solution)

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Answer: (b)

  1. Two surfaces: W=2TΔ(4πr2)=8πT(r22−r12)W = 2T \Delta(4\pi r^2) = 8\pi T (r_2^2 - r_1^2).
  2. With r1=d/2r_1 = d/2, r2=D/2r_2 = D/2: W=8πTD2−d24W = 8\pi T \dfrac{D^2 - d^2}{4}
  3. W=2π(D2−d2)TW = 2\pi (D^2 - d^2) T
  4. So the answer is (b) 2π(D2−d2)T2\pi(D^2-d^2)T.
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