An open glass tube is immersed in mercury in such a way that a length of 8 cm extends above the mercury level. The open end of the tube is then closed and sealed and the tube is raised vertically up by additional 46 cm. What will be length of the air column above mercury in the tube now? (atmospheric pressure =76 cm of Hg)

Options

A. 38 cm
B. 6 cm
C. 16 cm
D. 22 cm

Answer

C

Explanation

When glass tube is open, pressure inside it =`P_(0)`
When the open end of glass tube is closed, then pressure inside it = P'
`P'=P_(0)-rhogx" "...(i)`
Work done in case I = Work done in case II
Now, `P_(0)A(8)=P'A(54-x)`
`RightarrowP_(0)(8)=(P_(0)-rhogx)(54-x)" "[Using(i)]`
`Rightarrowrhog(76)(8)=rhog(76-x)(54-x)`
`76(8)=(76-x)(54-x)`
On solving x = 38 cm
Therefore, air column = `54-38=16cm`