Practice question
Question
What is the excess pressure inside a mercury drop of radius 2mm at 20∘C? (Surface tension of mercury = 0.465N/m)
Explanation
Excess pressure in a drop: ΔP = 2Sr. S = 0.465N/m, r = 2×10−3m. ΔP = 2×0.4652×10−3 = 465Pa. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 465 Pa. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.