Question

A U tube contains water and methylated spirit separated by mercury. The mercury columns in the two arms are at the same level with 10cm of water in one arm and 12.5cm of spirit in the other as shown in figure. The relative density of the spirit is

• A. 0.6
• B. 0.8
• C. 1.0
• D. 1.25

Answer 1

The correct option is B

0.8

As the mercury columns in the two arms of U tube are at the same level, therefore

Pressure due to water = Pressure due to spirit column
${\rho }_w{h}_{w}g={\rho }_s{h}_{s}g$

${\rho }_S=\frac{h_w}{h_s}{\rho }_w$

$\therefore$ Relative density of spirit = $\frac{{\rho }_s}{{\rho }_w}=\frac{h_w}{h_s}=\frac{10cm}{12.5cm}=0.8$