A U tube with both ends open to the atmosphere, is partially filled with water. Oil, which is immiscible with water, is poured into one side until it stands at a distance of 10 mm above the water level on the other side. Meanwhile the water rises by 65 mm from its original level (see diagram). The density of the oil is

Concept:

Manometers are the pressure measuring devices which measure the pressure at a point in a fluid. It is based on the principle of balancing of the column of the the fluid against the pressure. 

U tube Manometer- It is the transparent glass tube bent in U shape and both ends are open to the atmosphere.

Formula used to calculate pressure, P = h ρ g

where h and  ρ  is height of the column and density of the liquid respectively, g is acceleration due to gravity.

Calculation:

h_oil  ρ_oil g = h_water ρ_water g

140 × ρ_oil = 130 × ρ_water

ρ_oil = \(\frac{13}{14} \times 1000 kg/m^3\)

ρ_oil = 928 kg m^-3