A barometer tube of radius 1 mm contains mercury (surface tension 0.45 N/m and contact angle 143°). If atmospheric pressure is 75 cm of mercury column, what is height of mercury in the tube ρHg = 13.5 gm/cc.

Engineering

Physics

SI Units

Surface Tension and Surface Energy

Capillary and Pressure Difference due to Surface Tension

Question

A barometer tube of radius 1 mm contains mercury (surface tension 0.45 N/m and contact angle 143°). If atmospheric pressure is 75 cm of mercury column, what is height of mercury in the tube ρ_Hg = 13.5 gm/cc.

75 cm

75.4 cm

73.2 cm

74.6 cm

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$h = 75 - \frac{25 \cos 53 °}{rρg}$

$= 0.75 - \frac{2 \times 0.45 \times \frac{3}{5}}{10^{- 3} \times 13.5 \times 10^{3} \times 100}$

= 0.75 – 0.004
= 0.746 m