A spherical liquid drop of radius 2 mm and surface tension 0.05 N/m is divided into eight equal drops. If the increase in surface energy is Nπ × 10⁻⁷ J, find N.

Question

G1 Physics · Accepted Answer

For one drop split into n equal drops, W = 4πSR²(∛n−1). Here, n = 8, so ∛8 = 2. Thus, W = 4πSR². Substitute S = 0.05 N/m, R = 2 mm = 2×10⁻³ m. Therefore, W = 4π×0.05×(2×10⁻³)² = 4π×0.05×4×10⁻⁶ = 8π×10⁻⁷ J. Hence, N = 8.