Surface Tension (drop)

Question

Work required to increase surface area of a soap film by 0.02 m² (surface tension 0.03 N/m, film has two surfaces)?

RankGuru · Accepted Answer

1. **Surface Energy Concept**: Work done in increasing the surface area is stored as potential energy ($W = \gamma 	imes \Delta A_{total}$).
2. **Soap Film Geometry**: A soap film has **two surfaces** in contact with air. Therefore, for a reported change in area $\Delta A$, the total change in surface area is $2 \Delta A$.
3. **Calculation**:
   - $\gamma = 0.03$ N/m
   - $\Delta A = 0.02$ m²
   - $W = 2 	imes \gamma 	imes \Delta A$
   - $W = 2 	imes 0.03 	imes 0.02 = 0.0012$ J.
4. **Scientific Notation**: **$1.2 	imes 10^{-3}$ J**.

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Surface Tension (drop)

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