Topic: Fluid Mechanics
The pressure difference between the inside and outside of a liquid droplet of diameter 'd' due to surface tension (σ) is given by the relation
- A. ΔP = 4σ / d
- B. ΔP = 8σ / d
- C. ΔP = 2σ / d
- D. ΔP = 6σ / d
Answer: A. ΔP = 4σ / d
Explanation: For a liquid droplet, the surface tension force acts along the circumference, while the pressure force acts over the cross-sectional area. Equating these gives: P * (pi/4) * d² = σ * pi * d. Simplifying this yields the pressure difference ΔP = 4σ / d.