Calculating pressure changes in a liquid

4 minAS Level4.3.4

AI-drafted, independently checked · not yet teacher-reviewed

By the end of this lesson

By the end, you can use $\Delta p=\rho g\Delta h$ to find the pressure difference between two levels in a liquid.

The equation, in plain language

A deeper point has a greater pressure because more liquid sits above it. The pressure difference depends on how dense the liquid is, how far apart the levels are vertically and gravity's strength.

In the equation, $\Delta p$ means the pressure difference in pascals; $\rho$ is the liquid density in $\text{kg m}^{-3}$ ; $g=9.81\ \text{m s}^{-2}$ is acceleration of free fall; and $\Delta h$ is the vertical separation in metres. Then:

$\Delta p = \rho g\Delta h$

Quick check

CalculateQuestion 1 · Recall

What pressure difference is produced by a $0.50\ \text{m}$ vertical depth of water? Give your answer to 2 significant figures. Use $\rho=1000\ \text{kg m}^{-3}$ and $g=9.81\ \text{m s}^{-2}$ .

Pato 2 s.f.

Answer the 2 questions above to continue.

Previous lessonWhere the liquid-pressure equation comes from Next lessonUpthrust: pressure pushes back

Multiple choiceQuestion 2 · Recall

In the same stationary liquid, how does pressure change as vertical depth increases?

AIt increases.BIt decreases.CIt stays constant at every depth.