A thin solid square plate is placed gently on a liquid surface. The excess force required to lift the plate away from the surface is 12 mN . If the surface tension of the liquid is 0.06 N m ⁻¹ , the side length of the square plate is

Step-by-step solution

For a solid square plate, only the outer perimeter is in contact with the liquid surface. Total effective length of contact, L_ eff = 4a , where a is the side length of the plate. Excess force required, F = T L_ eff = T 4a 12 10⁻³ = 0.06 4a 4a = 12 10⁻³ 0.06 = 0.2 m a = 0.05 m = 5 cm Answer: 5 cm