Water and oil

Question

Water and oil (which don't mix) are poured into a U-shaped tube, open at both ends.  They come to equilibrium.  What is density of the oil?

 

 

the top of the tube is 8.62 cm and the oil side of the tube is 27.2 cm

Answer 1

Extend the oil-boundary line to the other side of the tube.  The pressure at this interface is the same for both sides of the U-tube at this line.

 

The pressure is due to the column of fluid above this line.

 

 

P_water = P_oil

 

ρ_watergh_water + P₀ = ρ_oilgh_oil + P₀

 

 

Solving for the density of oil,

 

ρ_oil = ρ_water h_water / h_oil = (1.00 g/ml)(8.62/27.2) = 0.317 g/ml