JEE MAIN - Physics (2014 (Offline) - No. 14)
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 scaled 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 $$Hg$$)
$$16$$ $$cm$$
$$22$$ $$cm$$
$$38$$ $$cm$$
$$6$$ $$cm$$
Explanation
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Length of the air column above mercury in the tube is,
$$P + x = {P_0}$$
$$ \Rightarrow P = \left( {76 - x} \right)$$
$$ \Rightarrow 8 \times A \times 76 = \left( {76 - x} \right) \times A \times \left( {54 - x} \right)$$
$$\therefore$$ $$x=38$$
Thus, length of air column $$=54-38=16cm.$$
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