Two glass plates are separated by water. If surface tension of water is 75 dynes per cm and area of each plate wetted by water is 8 cm² and the distance between the plates is 0.12 mm, then the force (in newton) applied to separate the two plates is
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Question

Two glass plates are separated by water. If surface tension of water is 75 dynes per cm and area of each plate wetted by water is 8 cm² and the distance between the plates is 0.12 mm, then the force (in newton) applied to separate the two plates is

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Infinity Learn · Accepted Answer

The shape of water layer between the two plates is shown in the figure.Thickness d of the film $$=$$ $$0.12$$ mm $$=$$ $$0.012$$ cm.Radius R of cylindrical face $$=$$ $$d2$$ F $$=$$ $$T(2l)$$ $$=$$ $$P(l$$× $$2R)$$ P $$=$$ TRPressure difference across the cylindrical surface $$=$$ TR $$=$$ $$2TdArea$$ of each plate wetted by water $$=$$ A.Force F required to separate the two plates is given $$byF=$$ pressure difference × area $$=2TdA=2$$×$$75$$×$$80.012=105dynes$$

Two glass plates are separated by water. If surface tension of water is 75 dynes per cm and area of each plate wetted by water is 8 cm² and the distance between the plates is 0.12 mm, then the force applied to separate the two plates is

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Two glass plates are separated by water. If surface tension of water is 75 dynes per cm and area of each plate wetted by water is 8 cm2 and the distance between the plates is 0.12 mm, then the force applied to separate the two plates is

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Two glass plates are separated by water. If surface tension of water is 75 dynes per cm and area of each plate wetted by water is 8 cm² and the distance between the plates is 0.12 mm, then the force applied to separate the two plates is