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Home » Mercury has an angle of contact equal to 140° with soda lime glass. A narrow tube of radius 1.00 mm made of this glass is dipped in a trough containing mercury. By what amount does the mercury dip down in the tube relative to the liquid surface outside ? Surface tension of mercury at the temperature of the experiment is 0.465 N m–1. Density of mercury = 13.6 × 103 kg m–3
Mercury has an angle of contact equal to 140° with soda lime glass. A narrow tube of radius 1.00 mm made of this glass is dipped in a trough containing mercury. By what amount does the mercury dip down in the tube relative to the liquid surface outside ? Surface tension of mercury at the temperature of the experiment is 0.465 N m–1. Density of mercury = 13.6 × 103 kg m–3
CBSE | Class 11 | Mechanical Properties of Fluids | NCERT | Physics
Mercury has an angle of contact equal to 140° with soda lime glass. A narrow tube of radius 1.00 mm made of this glass is dipped in a trough containing mercury. By what amount does the mercury dip down in the tube relative to the liquid surface outside ? Surface tension of mercury at the temperature of the experiment is 0.465 N m–1. Density of mercury = 13.6 × 103 kg m–3

Answer :

According to the question, the density of mercury is

ρ =13.6 × 103 kg/m3

Acceleration due to gravity, g = 9.8 m/s2
The angle of the contact between mercury and soda-lime glass is

θ = 140°
The surface tension of mercury at the given temperature

s = 0.465 N m-3
The radius of the narrow tube is

r = 2/2  = 1 mm = 1 × 10-3 m
Let h represent the dip in the depth of mercury. Therefore, we can write the expression of surface tension as follows :

S=\frac{hg\rho r}{2\cos \theta }

\Rightarrow h=\frac{2S\cos \theta }{g\rho r}

h=\frac{2\times 0.465\times \cos {{140}^{\circ }}}{13.6\times 9.8}

h=-5.34mm

The negative indication indicates that the mercury level is dropping. As a result, the mercury drops by 5.34 mm.

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