If ' $\mathrm{T}^{\prime}$ is the surface tension of a soap solution, then the work done in blowing a soap…

If ' $\mathrm{T}^{\prime}$ is the surface tension of a soap solution, then the work done in blowing a soap bubble from diameter 'D' to diameter '2D' is
  1. $2 \pi \mathrm{TD}^{2}$
  2. $4 \pi \mathrm{TD}^{2}$
  3. $8 \pi \mathrm{TD}^{2}$
  4. $6 \pi \mathrm{TD}^{2}$

Solution

$W=\frac{4 \pi}{4}\left(4 D^{2}-D^{2}\right) T \times 2$ $=3 \mathrm{D}^{2} \pi \mathrm{T} \times 2=6 \mathrm{D}^{2} \pi \mathrm{T}$

Asked in: MHT CET 2020 (20 Oct Shift 1)

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