Oil and water don’t mix, and the mass density of oil is smaller than that of water. Suppose water is poured into a U-shaped tube that is open at both ends until the water surface is halfway up each leg of the tube, and then some oil is poured on top of the water in the right leg. Once the system comes to equilibrium, are the top of the oil column in the right leg and the top of the water column in the left leg at the same height? If not, which is higher?
The right leg (oil on top) is higher
The left leg (no oil) is higher
The two legs are the same height

When we pour water in a u-tube that is open at both the ends then the water on both the sides of the tube will rise up to the same height because the algebraic sum of the pressure exerted by the water column and the pressure of atmosphere on both the openings is equal.

When we pour oil in the right side of the u-tube we observe that the column of liquid on the right side rises more than the column of the liquid on the left side. However we observe that there is rise on both sides of the u-tube.

This is justified by the equation:

[tex]P=\rho.g.h[/tex]

where:

[tex]\rho =[/tex] density of the liquid

[tex]g=[/tex] acceleration due to gravity

[tex]h=[/tex] height of the liquid column