Question

A U-tube in which the cross-sectional area of the limb on the left is one quarter, the limb on the right contains mercury (density 13.6 g/ $c{m}^3$). The level of mercury in the narrow limb is at a distance of 36 cm from the upper end of the tube. What will be the rise in the level of mercury in the right limb if the left limb is filled to the top with water

• A. 1.2 cm
• B. 2.35 cm
• C. 0.56 cm
• D. 0.8 cm

Answer 1

The correct option is C

0.56 cm

If the rise of level in the right limb be x cm. the fall of level of mercury in left limb be 4x cm because the area of cross section of right limb 4 times as that of left limb. $\therefore$Level of water in left limb is (36 + 4x) cm. Now equating pressure at interface of mercury and water (at A' B') (36 + 4x) $\times$ 1 $\times$ g = 5x $\times$ 13.6 $\times$g By solving we get x = 0.56 cm.