Question

The area of cross-section of the wider tube shown in figure is $800{\text{cm}}^2$. If a mass of $12\text{kg}$ is placed on the massless piston, the difference in heights $h$ in the level of water in the two tubes is (in $\text{cm}$) is

Answer 1

From pascals law,
$P_A=P_B$
$[\frac{mg}{A}=\rho gh]$
$\frac{12\times {10}^3\text{gm}}{800{\text{cm}}^2\times 1{\text{gm/cm}}^3}=h$
$h=15\text{cm}$