Some mercury is poured into a capillary tube of uniform bore and one end closed. When the tube is held horizontally, mercury column has a length of 4 cm and air enclosed in the closed end has a length of 10 cm. If the tube is now held vertically, with open end upwards, the length of the air column will be (take atmospheric pressure at the place of experiment to be 760 mm)

Options

A. 10.5 cm
B. 8.5 cm
C. 9.0 cm
D. 9.5 cm

Answer

D

Explanation

When held horizontally, pressure of enclosed air =760 mm
When held vertically, pressure increases by 4 cm, i.e., 40 mm
Hence, now pressure=760+40=800 mm
Applying `P_(1)V_(1)=P_(2)V_(2)`
`P_(1)xx(Axxl_(1))=P_(2)xx(Axxl_(2))`
(A=area of cross-section of the capillary tube)
or `P_(1)xxl_(1)=P_(2)xxl_(2)`
`760xx10=800xl_(2)" or "_(2)=9.5" cm"`