The work done against surface tension in blowing a soap bubble from a radius 10 cm to 20 cm if the surface tension of solution is 25 × 10

Engineering

Physics

Surface Tension

Question

The work done against surface tension in blowing a soap bubble from a radius 10 cm to 20 cm if the surface tension of solution is 25 × 10^–3 N/m is -

2π × 10^–3 J

3π × 10^–3 J

6π × 10^–3 J

4π × 10^–3 J

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Initial total surface area,
A₁ = 2 × 4π (0.1)²m²
Final total surface area,
A₂ = 2 × 4π (0.2)²m²
Work done against surface tension, W = S(A₂ – A₁)
W = 25 × 10^–3 × 8π (0.04 – 0.01) = 6π × 10^–3 J

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