O-Level Physics Error & Uncertainty Masterclass

TL;DR\ SEAB’s 2026 Physics syllabus expects you to quote readings to the correct precision, propagate uncertainties, and discuss limitations for ACE. Use absolute + percentage uncertainties, keep significant figures consistent with instrument resolution, and tie every ACE statement to how an error changes your conclusion.\ Build a commentary template: state result ± uncertainty, compare with a reference value if provided, identify the dominant error, and propose a realistic fix that would reduce that error.

Keep Your Physics Practical Stack On Track

Use our O-Level Physics Experiments hub to find companion drills for every Paper 3 skill before you attempt these walkthroughs.

1 | Precision rules every candidate must memorise

• Instrument dictates precision: Quote to the smallest division of the instrument. The 6091 apparatus list includes rules with a millimetre scale, digital calipers (0.01 mm), digital micrometers (0.001 mm), and stopwatches (0.1 s or better).\
• Write what you record: Raw tables must show units in headings (Length / cm) and use consistent decimal places aligned with the measuring tool.\
• Calculated quantities follow the weakest link: When you compute density, resistance, or refractive index, round to the same number of significant figures as the least precise raw input.

✅ Quick check: before leaving a table, scan the decimal places column by column. Any mix like 12.0 vs 12.00 means a lost mark in PDO.

2 | Uncertainty toolkit (with sample numbers)