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

SI Units

Surface Tension and Surface Energy

Capillary and Pressure Difference due to Surface Tension

Question

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.

cos^–1 (1/2)

cos^–1 (3/4)

37°

cos^–1 (3/7)

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$h = \frac{2 scos θ}{rρg}$

$\frac{h}{\cos θ} = \frac{ℓ}{\cos θ}$

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

$\cos θ = \frac{3}{4}$