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Q: What does IP Physics Plasticine: 7 Experiments that Turn Soft Clay into Hard-Won Marks cover? A: Malleable, cheap and exam-friendly, plasticine is the stealth MVP of IP and H2 Physics practical work.
TL;DR Plasticine's super-power is that it can be reshaped in seconds, sticks to things on impact and sinks slowly in syrup. Those three traits unlock at least seven physics ideas-from density checks to perfectly inelastic collisions-that frequently appear in IP weighted assessments and H2 practical papers. This article lays out the exact mini-labs, common slip-ups and a 5-day micro-practice plan so you can turn a $2 block of clay into solid grades.
Stokes' Law is not listed as required knowledge in the current IP Physics or H2 Physics syllabuses. Examiners may, however, supply unfamiliar relationships (including Stokes'drag) in an open-ended design or data-handling question and ask you to derive or apply them using provided graphs or first-principles ideas. Memorising the Stokes'Law equation is therefore optional - keep sub-section 2.2 as an enrichment task, or skip it entirely if you prefer to focus strictly on examinable content.
Keep your practice loop tight via our IP Physics tuition hub-it links each topic here to quizzes, diagnostics, and WA-style problem sets.
1 Why every H2 lab issues a lump of plasticine
Malleable & re-usable - one block can be rolled into spheres, flattened into pucks or packed onto carts in seconds.
Safe & classroom-friendly - no shards, no bounce, no toxic dust.
Density ≈1.4g⋅cm−3
Lab venues
Practical sessions run at our partner lab venues (not at the theory tuition centres).
-heavy enough to sink in water yet light enough to reach terminal velocity in a 1 m-tall syrup column.
Sticky on impact - guarantees a perfectly inelastic collision every time, a requirement in many momentum tasks.
IP exam setters exploit those virtues because they let students focus on data handling and uncertainty, not tricky apparatus.
These guides track SEAB GCE O-Level Physics (6091) scope (exams from 2026) with IP-focused practical emphases.
Status: SEAB O-Level Physics 6091 syllabus/practical skills (exams from 2026) checked 2025-11-30 - scope unchanged; use school lab briefings for ordering of topics.
2 Seven physics ideas a clay lump can prove
2.1 Density without Archimedes
Roll five different-mass spheres, measure mass (digital balance) and diameter (vernier calliper). A log-log mass-vs-diameter³ plot gives the density as the gradient. Students spot linearisation and propagate percentage uncertainties in one go.
2.2 Stokes' law in a jam jar
Drop the spheres through glycerine or honey, time the last 10 cm fall. Plot radius² against terminal velocity; gradient yields the fluid viscosity via vt=92η(ρsphere−ρfluid)gr2. A single kitchen jar turns into an H2-level viscometer.
2.3 Perfectly inelastic collisions on a bench-top
Load a rolling dynamics cart with a motion sensor, fire a plasticine bullet from a spring launcher. The bullet sticks; momentum is conserved but kinetic energy drops-students calculate the lost KE and discuss energy pathways.
2.4 Centre of mass & counter-intuitive balance
Shift tiny lumps along a ruler until it balances on a pencil; plot distance-of-lump vs centre-of-mass position to verify the lever rule. A neat visual for stability questions.
2.5 Elastic vs plastic deformation
Clamp a strip of plasticine and hang masses; strain rises but never returns-an instant demo of plastic region beyond Hooke's law. Compare to a steel spring on the same rig.
2.6 Rolling friction & energy dissipation
Roll an iron ball into a plasticine target on a smooth track; measure the embed depth to estimate the work done by rolling friction. AAPT's experiment shows how multiple concepts intertwine.
2.7 Pressure imprint mapping
Press a loaded test-tube onto a plasticine pad; the contact area reveals pressure distribution-great for qualitative questions on pressure = force/area.
3−5 plasticine spheres, radii 3mm−7mm, measured with a vernier calliper.
Electronic balance ±0.01g.
Cooking oil (≈0.065Pas at 25∘C).
Digital thermometer ±0.1∘C clipped midway down the column.
Stopwatch capable of 0.01s or phone camera 120 fps for video timing.
Step-by-step method (justified)
Calibrate & condition: Warm the oil bath to 25±0.5∘C and stir gently to ensure uniform temperature (controls viscosity).
Measure sphere mass & diameter three times each; compute mean radius and density to ±1%.
Release protocol: Hold the sphere with tweezers at centreline to avoid wall effects, then let go without imparting spin.
Timing window: Start timer 5 cm below the oil surface (allows acceleration phase to finish) and stop 25 cm lower. Distance is marked with masking tape for consistency.
Repeat for each radius thrice; discard trials where the sphere touches the wall or creates visible wake (possible Re>1).
Clean-up: Retrieve spheres with perforated spoon; wash glassware with detergent, dry, store. Follow glassware safety to prevent breakage.
Uncertainty & error analysis
Random: reaction-time error (~0.2 s) divides by long timing distance, so percent uncertainty ≈0.2s/4s≅5%. Reduce by video analysis.
Systematic: ignoring buoyancy term overestimates η by ≈10%. Always subtract ρoil from ρsphere.
Wall effect: keep cylinder diameter ≥ 10 x sphere diameter to keep correction <1%.
Temperature drift: viscosity of vegetable oils changes ≈2−3%K−1; record bath temperature every two trials.
Apply propagation of uncertainty formally (GUM) when reporting η.
Typical data & sample calculation
For a 5.00mm radius sphere (mass = 0.52g) falling 0.25m in 3.60s at 25∘C:
Literature viscosity for canola oil at 25∘C≈0.067Pa⋅s - within 4% of accepted value.
Validity checks & improvement ideas
Check linearity: plot v against r2; R2>0.99 confirms Stokes regime.
Lower Re further: use smaller spheres or colder oil if curvature appears.
Automate timing with Light-Gate + Data-logger to cut human reaction error to < 1%.
Compare liquids: run the same spheres in water and glycerine to highlight viscosity contrast and reinforce concept transfer.
4 Common mistakes & lightning fixes
Slip-up
Why it hurts
Fix in 10 s
Forgetting buoyancy term in Stokes analysis
Over-estimates viscosity by 10%
Write ρsphere−ρfluidfirst, highlight in colour
Calling collision “elastic” because carts rebound slightly
Loses theory marks
Stick an extra sliver of clay to guarantee zero rebound
Measuring sphere diameter with a ruler
±1mm error dominates
Use a vernier; take three perpendicular readings
Rounding mid-calculation
Data scatter inflates
Keep one extra s.f. until final line
5 5-Day micro-practice sprint
Day
15-min mission
Concept locked
1
Roll 3 spheres, plot mass vs diameter3
Density & linearisation
2
Drop one sphere in honey, record video at 120 fps
Terminal velocity
3
Glue clay to air-track glider, do a sticky collision
Momentum conservation
4
Balance a ruler with clay lumps, sketch CoM shift
Centre of gravity
5
Quiz yourself: list every uncertainty source seen
PDO reflex
Tick each box, snap a photo, post to class chat-peer accountability matters.
6 Quick FAQ
Q Why does IP love “plasticine questions”? Because the same blob lets exam writers weave density, kinematics and mechanics into one neat package, mirroring the cross-topic flavour of A-Level practicals.
Q Won't the clay absorb oil and change mass? Mass change over a 30s run is <0.1% - well inside typical measurement uncertainty.
Q Is Blu-Tack a valid substitute? Blu-Tack is visco-elastic; rebound spoils perfectly inelastic assumptions. Stick to plasticine.
