TL;DR Paper 3 explicitly lists measurement, density, (g), and moments investigations as core practical experiences for 6091 Physics in 2026 (SEAB syllabus). MMO marks hinge on disciplined instrument handling - calipers, micrometers, balances, spring balances, and stopwatches all appear in the six mechanics tasks. ACE credit comes from linking gradients, intercepts, and systematic effects to the mechanics concepts that the syllabus expects (forces equilibrium, torque balance, free-fall model).
1 | Measurement toolkit spotlighted by SEAB
The 2026 syllabus requires candidates to measure length, volume, mass, temperature, current, and voltage with standard lab instruments before they tackle any mechanics investigation (items 1–2, SEAB 2026 Physics syllabus).
Practise density determinations for regular and irregular solids that sink in water - examiners expect buoyancy corrections, displaced-volume readings, and significant-figure discipline (item 2, SEAB 2026 Physics syllabus).
Calibrate balances and spring balances before recording measurements, and note zero-error corrections because Planning (P) marks reward risk controls (SEAB 2026 Physics syllabus).
Instrument
MMO focus
PDO / ACE reminders
Tapes / rules / calipers
Align scale centrally and quote to 0.1 cm or 0.01 cm depending on instrument.
Record zero offsets, repeat along perpendiculars, and compute average diameters for density or moment arms.
Micrometers
Check ratchet clicks for consistent pressure.
Apply zero-error correction before averaging; express radius/diameter with propagated uncertainty in ACE commentary.
Measuring cylinders
Read at eye level, avoid meniscus parallax.
For density work, tabulate mass alongside volume and compute (\rho = m/V) with consistent units (g cm⁻³ or kg m⁻³).
Balances / spring balances
Tare containers and confirm capacity limits.
Note maximum loads, mention vibration damping, and justify choice of balance range in planning responses.
Stopwatches
Practise timing 10–20 oscillations or periods.
Discuss reaction-time uncertainty and the benefit of multi-period timing when analysing (g) or dynamic measurements.
2 | Mechanics investigations that recur in Paper 3
2.1 | Determining the acceleration of free fall (g)
The syllabus lists a dedicated (g) determination (item 3, SEAB 2026 Physics syllabus). Be ready to linearise s=0.5,g,t2 or use pendulum timing.
Planning: describe how you measure displacement or length, the number of repeats, and how you mitigate launch height errors.
MMO: keep release height fixed, use electronic timing where supplied, and note safety (clear fall path).
PDO / ACE: tabulate (t) and (t^2), plot (s) against (t^2), and justify any gradient-based estimate of (g).
2.2 | Balanced and unbalanced forces
SEAB expects experiments exploring equilibrium and resultant forces (item 4, SEAB 2026 Physics syllabus). Typical setups include Newton meters with angled strings or trolleys on slopes.
Planning: cite friction mitigation (smooth runway, light gates) and describe how you vary a single parameter.
ACE: comment on frictional losses, pulley mass, or string stretch - improvements could include using a ticker timer or data logger for consistent acceleration readings.
2.3 | Principle of moments and centre of gravity
The principle of moments (item 5) and centre of gravity determinations (item 6) remain staple tasks (SEAB 2026 Physics syllabus).
MMO: ensure pivot points are sharply defined, measure perpendicular distances, and add weights symmetrically.
PDO: tabulate clockwise and counterclockwise moments with units (N cm).
ACE: explain how small angular displacement or weight hook thickness affects torque accuracy, and propose using thinner hooks or mirror scales to reduce parallax.
2.4 | Density of solids and liquids
Density tasks (item 2) bridge measurement with mechanics because they often precede buoyancy or pressure experiments (SEAB 2026 Physics syllabus).
Show how you dry irregular solids before volume displacement, state that water temperature should be constant, and mention corrections for air bubbles.
Present mass–volume tables with consistent units and compute mean densities, flagging outliers or systematic offsets.
3 | Planning and ACE checklists tailored to mechanics
Refer to all four assessed skill strands - P, MMO, PDO, ACE - when drafting plan responses, because Paper 3 can embed planning elements inside measurement tasks (SEAB 2026 Physics syllabus).
Quantify uncertainties: quote ruler precision (±0.1 cm), stopwatch reaction time (±0.1 s), and balance resolution (±0.01 g).
State realistic improvements such as using fiducial markers for motion timing, digital scales with higher resolution, or clamped protractors when measuring angles.
Align safety precautions with MOE’s science laboratory guidelines - secure masses, keep the area clear of trip hazards, and store weights after use (MOE laboratory safety guide).
4 | Mechanics practice prompts between lab sessions
(g) plotting drill: Collect pendulum times for lengths 40–90 cm, plot (T^2) vs (L), and extract (g) from the gradient; write an ACE paragraph explaining how timing jitter affects the slope.
Moments investigation: Build a metre-rule balance with unequal masses, measure arm lengths, and compute clockwise vs counterclockwise moments; discuss how hook thickness changes lever-arm measurements.
Density audit: Measure three irregular metal pieces, record mass, displaced water volume, and compute density; explain deviations from handbook values by referencing entrapped bubbles or misread menisci.
