Question

A barometer tube reads $76\text{cm}$ of $\text{Hg}$. If the tube is gradually inclined at an angle of ${30}^{\circ }$ with horizontal, then find the length of the mercury column in the barometer tube.

• A. $142\text{cm}$
• B. $152\text{cm}$
• C. $132\text{cm}$
• D. $122\text{cm}$

Answer 1

The correct option is B $152\text{cm}$

We know that barometer is used to measure atmosphere pressure.
Given, atmospheric pressure, $P_o=76\text{cm}$ of $\text{Hg}$
$\Rightarrow h=76\text{cm}$

When the tube is inclined, then the vertical height of the mercury column will remain the same as atmospheric pressure is the same.

From figure, $l\sin {30}^{\circ }=76$
$\Rightarrow l=\frac{76}{\sin {30}^{\circ }}=152\text{cm}$