An open-ended U-tube of uniform cross-sectional area contains water (density $10^3 \mathrm{~kg} \mathrm{~m}^{-3}$ ). Initially the water level stands at 0.29 m from the bottom in each arm. Kerosene oil (a water-immiscible liquid) of density $800 \mathrm{~kg} \mathrm{~m}^{-3}$ is added to the left arm until its length is 0.1 m , as shown in the schematic figure below. The ratio $\left(\frac{h_1}{h_2}\right)$ of the heights of the liquid in the two arms is-
Select the correct option:
A
$\frac{15}{14}$
B
$\frac{35}{33}$
C
$\frac{7}{6}$
D
$\frac{5}{4}$
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
Sol.
$$
\begin{aligned}
h_1 & +h_2=0.29 \times 2+0.1 \\
h_1 & +h_2=0.68 \\
\Rightarrow & P_0+\rho_k g(0.1)+\rho_w g\left(h_1-0.1\right)\left[\rho_k=\text { density of kerosene } \& \rho_w=\text { density of water }\right] \\
& -\rho_w g h_2=P_0 \\
\Rightarrow & \rho_k g(0.1)+\rho_w g h_1-\rho_w g \times(0.1) \\
& =\rho_w g h_2 \\
\Rightarrow & 800 \times 10 \times 0.1+1000 \times 10 \times h_1 \\
& -1000 \times 10 \times 0.1=1000 \times 10 \times h_2 \\
\Rightarrow & 10000\left(h_1-h_2\right)=200 \\
\Rightarrow & h_1-h_2=0.02 \\
\Rightarrow & h_1=0.35 \\
\Rightarrow & h_2=0.33
\end{aligned}
$$
So, $\frac{\mathrm{h}_1}{\mathrm{~h}_2}=\frac{35}{33}$
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