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CAIE A-Level Physics 4.3.4 Hydrostatic Pressure Change

Practise applying delta p = rho g delta h to liquids, manometers and depth graphs, distinguishing pressure differences from absolute pressure.

Syllabus
2028–2030
Course
Physics 9702
Level
AS

Exam points

  • apply Δp = ρgΔh to calculate a pressure difference across a fluid depth
  • rearrange Δp = ρgΔh to determine density, depth or gravitational field strength from measured data
  • interpret pressure differences in connected or layered fluids, distinguishing a pressure difference from the absolute pressure when the question requires it

4.3.4—The equation ∆p = ρg∆h question 1

[Maximum number: 3]

A beaker in air contains a liquid. The base of the beaker is in contact with the liquid and has area A, as shown in Fig. 4.1.

Fig. 4.1

Fig. 4.1

The liquid has density ρ\rho and fills the beaker to a depth h.

Fig. 4.2 shows the variation of the total pressure inside the liquid with depth x below the surface.

Fig. 4.2

Fig. 4.2

Determine the density of the liquid.
density = kgm−3\mathrm{kg} \mathrm{m}^{-3}

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