When a glass capillary tube is immersed in a liquid, the latter rises to a height of 6mm. The tube is gradually pressed down, until a length of only 4 mm projects outside. The liquid meniscus makes an angle of 60° with the walls of the capillary. Determine the angle of contact for the glass and the liquid pair.

Engineering

Physics

Surface Tension

Question

cos^–1 (1/2)

cos^–1 (3/4)

37°

cos^–1 (3/7)

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$h = \frac{2 scos θ}{rρg}$

$\frac{h}{\cos θ} = \frac{ℓ}{\cos θ}$

$\frac{6}{\cos θ} = \frac{4}{\cos 60^{\circ}}$

$\cos θ = \frac{3}{4}$

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