Paper 3 at a glance
- Paper 3 carries 15 marks
Experiment: How the depth of a liquid affects the pressure
To investigate the relationship between the depth below the surface of a liquid and the pressure at that depth.
- Manipulated: Depth below the liquid surface, h
- Responding: Pressure, shown by the height difference in the manometer, H
- Constant: The same liquid (same density)
- Graph: Plot H (pressure, y-axis) against depth h (x-axis). A straight line through the origin shows the pressure is directly proportional to the depth.
- Analysis: The pressure in a liquid is given by P = hρg, so it increases in direct proportion to the depth. Turning the membrane to face different directions at the same depth shows the pressure acts equally in all directions.
Experiment: Measuring gas pressure with a liquid manometer
To determine the pressure of a gas supply using a liquid column manometer.
- Manipulated: Setting of the gas supply (flow rate)
- Responding: Height difference of the liquid columns, h
- Constant: Atmospheric pressure and the density of the manometer liquid
- Graph: A graph is optional. If several settings are used, the gas pressure can be compared with the height difference h to show that a greater h means a greater gas pressure.
- Analysis: When the gas pushes the liquid down on its side, the gas pressure P(gas) = P(atmospheric) + hρg. Convert h to a pressure using hρg and add the atmospheric pressure to obtain the gas pressure.
Paper 3 skill checklist
- Table: quantities with units in the headings, consistent decimal places, derived column calculated correctly.
- Graph: axes labelled with unit, scale using more than half the grid, points plotted with a sharp pencil, best-fit line.
- Gradient: a large triangle on the line, coordinates shown, unit of the gradient stated.
- Relationship: "y increases linearly with x" or "y is directly proportional to x" only if the line passes through the origin.
- Precaution: one that improves accuracy, stated with its reason.
More on graph skills
Exam tip
Units on every calculation line; no formula is provided in the SPM Physics papers.
More Pressure resources
- Chapter overview: Pressure
- Revision Notes
- Common Mistakes
- Practice Questions
- Paper 2 Answering Guide
- Key Terms
- Calculation practice sets
Source: DSKP KSSM Physics Form 4 and 5 (Versi English), Sijil Pelajaran Malaysia: Format Pentaksiran mulai 2021, Fizik (4531) (Bahagian Pembangunan Kurikulum (BPK), KPM)
Written by the spmphysics.com.my editorial team.· Updated 5 Sept 2026