Question

Given $P_{atm}=76\text{cm of Hg}$.
Find the length of the air column trapped in fig - 2

• A. 10.85 cm
• B. 11.25 cm
• C. 12.85 cm
• D. 11.75 cm

Answer 1

The correct option is A 10.85 cm

Since, $n$ and $T$ are constants, $PV=\text{const.}$
Say Area of cross section is $A$, then :
$(12\text{cm}\times A)\times 76\text{cm}=(l\times A)\times 84\text{cm}$
$l=12\times \frac{76}{84}=10.85\text{cm}$