Answer:
20.4 cm; 2.4 cm
Explanation:
The formula for the pressure p exerted by a column of a liquid with density ρ and height h is
p = ρgh
where h = the acceleration due to gravity
If you have two liquids balancing each other in a U-tube
p₁ = p₂
ρ₁gh₁ = ρ₂gh₂
ρ₁h₁ = ρ₂h₂
Data:
ρ₁ = 1010 kg/m³; h₁ = 18 cm
ρ₂ = 890 kg/m³; h₂ = ?
1. Height of oil column
We measure from the horizontal red line.
[tex]\begin{array}{rcl}\rho_{1}h_{1} & = &\rho_{2}h_{2}\\\text{1010 kg/m}^{3} \times \text{18 cm} & = & \text{890 kg/m}^{3} \times h_{2}\\\text{18 180 cm} & = & 890h_{2}\\h_{2} & = & \dfrac{\text{18180 cm}}{890}\\\\ & = & \text{20.4 cm}\\\end{array}\\ \text{The height of the oil column is $\textbf{20.4 cm}$}[/tex]
2. Height of oil above water
h₂ - h₁ = 20.4 cm – 18 cm = 2.4 cm
