Practice question
Question
What is the excess pressure inside a water drop of radius 2.5mm at 20∘C? (Surface tension = 0.0727N/m)
Explanation
Excess pressure: ΔP = 2Sr. S = 0.0727N/m, r = 2.5×10−3m. ΔP = 2×0.07272.5×10−3 = 58.16Pa. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 58 Pa. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.