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#Laplace pressure

4 public questions tagged with this topic.

What is the excess pressure inside an ethanol drop of radius 1.5mm at 20∘C? (Surface tension = 0.0227N/m)

Excess pressure: ΔP = 2Sr. S = 0.0227N/m, r = 1.5×10−3m. ΔP = 2×0.02271.5×10−3 = 30.27Pa. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 30 Pa. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.

Ref: NCBI Bookshelf, Ideal Gas Law: P1V1/T1 = P2V2/T2.

A soap bubble of radius 9mm has a surface tension of 0.026N/m. What is the excess pressure inside?

Excess pressure in a bubble: ΔP = 4Sr. S = 0.026N/m, r = 9×10−3m. ΔP = 4×0.0269×10−3 = 11.56Pa. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 11.5 Pa. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.

Ref: NCBI Bookshelf, Ideal Gas Law: P1V1/T1 = P2V2/T2.

A soap bubble of radius 12mm has a surface tension of 0.024N/m. What is the excess pressure inside?

Excess pressure in a bubble: ΔP = 4Sr. S = 0.024N/m, r = 12×10−3m. ΔP = 4×0.02412×10−3 = 8Pa. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 8 Pa. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.

Ref: NCBI Bookshelf, Ideal Gas Law: P1V1/T1 = P2V2/T2.