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physics.fisikatudycenter.com - how to find the densities or heights of fluids in U-tube. Some cases in U-tube involve more than two kinds of fluid. Read the cases below:

U-tube fills three kinds of fluid, 1, 2 and 3. What is the equation for that case? Use a line as a reference (shown in the figure), point A in the left arm and point B in the right arm (fluid 1-fluid 2 interface) are at the same level. So the pressure ar poin A and the pressure at point B must be the same. Easily we arrange the equation for this case, remember again the pressure of fluid at the depth of h, P = ρ g h

P_A = P_B
P₁ = P₂ + P₃
ρ₁ g h₁ = ρ₂ g h₂ + ρ₃ g h₃

We could cancel the g so then

ρ₁ h₁ = ρ₂ h₂ + ρ₃ h₃

Use this equation to determine what you need in here.

With the same way we will get the equation for U-tube with four fluids in it



P_A = P_B
P₁ + P₄ = P₂ + P₃
ρ₁ g h₁ + ρ₄ g h₄ = ρ₂ g h₂ + ρ₃ g h₃

Cancelling the g so then

ρ₁ h₁ + ρ₄ h₄ = ρ₂ h₂ + ρ₃ h₃

Finally, insert your data!