Question

A container is filled to a depth of 20.0 cm with water. On top of the water floats a 30.0-cm-thick layer of oil with a specific gravity of 0.700. What is the absolute pressure at the bottom of the container?

Short answer

The absolute pressure at the bottom of the container is; $P_{absolute}=1.05\times {10}^5\text{pa}$

Step-by-step solution

Given Data

Thickness of air$=30cm$

Thicknessofwater$=20cm$

Specific gravity of air$=0.700$

Concept

Theexcesspressure,generallyknownasgaugepressure,isgivenby:

$P_{gauge}=\rho gh$

The absolute pressure at the bottom of the container is given by:

$P_{absolute}=$Pressure due to water + pressure due to air + atmospheric pressure

Find the absolute pressure at the bottom of the container.

$$\begin{gathered} P_{absolute}={\rho }_{w}g{h}_w+{\rho }_{Air}g{h}_{air}+P_{atm} \\ {P}_{absolute}=1000\times 9.8\times 0.2+700\times 9.8\times 0.3+1.01\times {10}^5 \\ {P}_{absolute}=1.05\times {10}^5\text{pa} \end{gathered}$$

Hence, the absolute pressure at the bottom of the container is $P_{absolute}=1.05\times {10}^5\text{pa}$;