Practice question
Question
What is the excess pressure inside a water drop of radius 1.8mm at 20∘C? (Surface tension = 0.0727N/m)
Explanation
Excess pressure: ΔP = 2Sr. S = 0.0727N/m, r = 1.8×10−3m. ΔP = 2×0.07271.8×10−3 = 80.78Pa. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 80 Pa. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.
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