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CAIE A-Level Physics AS 4.3 Density and Pressure Questions

Practise calculating density, pressure and hydrostatic changes, explaining upthrust and applying Archimedes’ principle to floating or suspended bodies.

Syllabus
2028–2030
Course
Physics 9702
Level
AS

Exam points

  • use ρ = m/V to calculate or compare density, mass and volume for solids, liquids or composite materials
  • calculate pressure from force and area and use Δp = ρgΔh for a fluid column or pressure difference
  • explain hydrostatic pressure and derive or apply its dependence on density, gravitational field strength and depth
  • explain the origin of upthrust from the pressure difference across an immersed object
  • calculate upthrust with F = ρgV and apply Archimedes’ principle with force balance to floating or suspended bodies

Covered syllabus points

4.3.1—Density4.3.2—Pressure4.3.3—Derive, from the definitions of pressure and density, the equation4.3.4—The equation ∆p = ρg∆h4.3.5—The upthrust acting on an object in a fluid is due to a difference in4.3.6—The upthrust acting on an object in a fluid using the equation F = ρgV

Question 1

[Maximum number: 1]

The diagram shows the arrangement of atoms in a particular crystal.

Figure for Question 1 — CAIE A-Level Physics AS

Each atom is at the corner of a cube.
The mass of each atom is 3.5×10−25 kg3.5 \times 10^{-25} \mathrm{~kg}. The density of the crystal is 9.2×103 kg m−39.2 \times 10^{3} \mathrm{~kg} \mathrm{~m}^{-3}.
What is the shortest distance between the centres of two adjacent atoms?

A

3.8×10−29 m3.8 \times 10^{-29} \mathrm{~m}

B

6.2×10−15 m6.2 \times 10^{-15} \mathrm{~m}

C

3.4×10−10 m3.4 \times 10^{-10} \mathrm{~m}

D

3.0×10−9 m3.0 \times 10^{-9} \mathrm{~m}

Question 2

[Maximum number: 1]

Which expression for pressure is correct?

A

force per unit area

B

mass per unit area

C

mass per unit volume

D

weight per unit volume

Question 3

[Maximum number: 1]

The derivation of the pressure equation Δp=ρgΔh\Delta p=\rho g \Delta h uses a number of relationships between quantities.

Which relationship is not used in the derivation of this equation?

A

density = mass  volume =\frac{\text { mass }}{\text { volume }}

B

potential energy = mass × acceleration of free fall × height

C

pressure = force  area =\frac{\text { force }}{\text { area }}

D

weight = mass × acceleration of free fall

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