In given figure, if the pressure of gas in bulb $$A$$ is $$50$$ $$cm$$ $$Hg$$ vacuum and $${P_{atm}} = 76\,cm\,Hg,$$ then height of column $$H$$ is equal to

Refer to figure, the absolute pressure of gas $$A$$ in the bulb is

The force $$F$$ needed to support the liquid of density $$d$$ and the vessel on top (fig) is

The cross-sectional area of one limb of a U-tube manometer [ Figure shown below ] is made $$500$$ time larger than the other, so that the pressure difference between the two limbs can be determined by measuring $$'h'$$ on one limb of the manometer. The percentage error involved is :