Ten IP Math & Physics Misconceptions — Debunked
Download printable cheat-sheet (CC-BY 4.0)10 Jul 2025, 00:00 Z
TL;DR Misconceptions arise whenever lessons move too fast to let students test assumptions.
This post spotlights ten of the most stubborn myths we meet in Eclat classrooms, shows how each one hurts grades, and supplies rapid-fire antidotes you can try after dinner.
1 Why misconceptions matter more in the IP track
- Compressed timeline — IP pulls selected A-Level ideas down to Sec 3-4, so shaky basics snowball faster.
- Inter-topic questions — a false belief in one topic (e.g. "gravity only acts downwards") wrecks multi-step proofs combining energy, vectors and calculus.
- Inquiry assessments — design-and-data tasks mark reasoning, not recall; a hidden misconception bleeds marks across Method, Discussion and ACE bands.
See our earlier deep dives on these pressures in Why Sec 3 IP Students Struggle and Underperforming in IP.
2 Top-10 misconceptions & two-minute fixes
| # | Misconception | Why it's wrong | Quick fix |
| 1 | "Vectors are just numbers with arrows." | Vectors obey different algebra: \(\vec a + \vec b \neq \vec b + \vec a\). Direction changes signs and affects dot / cross products. | Make students write components before magnitude: \((3,4)\) then \(\sqrt{3^2+4^2}\). |
| 2 | "A negative area under a \(v-t\) graph is impossible." | Negative area means displacement opposite the positive axis, not 'no area'. | Sketch a runner reversing — shade area below axis to visualise backward travel. |
| 3 | "Current is used up by components." | Charge carriers flow in a loop; energy converts, current stays equal in series. | Use ammeters before and after a bulb; readings match within \(\pu{0.01 A}\). |
| 4 | "\(f(x+h) - f(x)\) is always small, so can be ignored." | For derivatives, the ratio with \(h\) matters; cancelling 'small' terms prematurely kills the limit. | Work one full first-principles proof for \(f(x)=x^2\). |
| 5 | "Gravitational field strength \(g\) is \(\pu{9.81 m.s-2}\) everywhere." | \(g\) drops with altitude and varies with latitude. | Calculate \(g\) on a \(\pu{1 km}\) high hill using \(g\propto1/r^2\). |
| 6 | "Significant figures only matter in the final answer." | Early rounding skews gradients, logs and percentage error. | Keep one extra s.f. in intermediate lines; round only in the last step. |
| 7 | Square roots "are always positive." | The square-root function \( \sqrt{k} \) is conventionally defined to return the principal (non-negative) root. When you solve an equation of the form \(x^2=k\) with \(k>0\), arithmetic demands both solutions, \(x=\pm\sqrt{k}\). | Whenever you extract a root while solving, write the explicit "\(\pm\)" sign before substituting numbers, then place the principal-root symbol only inside calculations that truly need the non-negative value. |
| 8 | "Momentum is conserved only in elastic collisions." | Momentum conserves in all isolated systems; kinetic energy conserves only in elastic cases. | Smash a plasticine ball into a cart (perfectly inelastic) and calculate \(p\) before/after. |
| 9 | "If two events are independent, they must be mutually exclusive." | Independence ≠ exclusivity; events can overlap yet probabilities multiply. | Draw a Venn diagram of tossing two coins — heads on coin 1 ∩ heads on coin 2. |
| 10 | "Logarithm of a product is equal to the product of the logarithms." | Taking the logarithm of a product is equal to the sum of the logarithms: \(\log(AB) = \log A + \log B\); logarithm of a division becomes subtraction of logarithms. | Have students verify with \(\log_{10} (8/2) = 0.602… = \log8- \log2\). |
3 Mini-case study: How one myth shreds marks
Scenario A Sec 3 student assumes current drops after every resistor because "the bulb uses it up".
Ripple effect
- Draws unequal current arrows in a series loop — loses 1 mark in FBD.
- Applies \(V=IR\) with wrong \(I\) — algebra spirals, loses Method marks.
- Discussion section claims "current difference explains dimmer bulb." Physics falls apart.
15-minute rehab
- Parallel demo: identical ammeters on either side of a \(\pu{6.0 V}\) lamp show \(I_1 \approx I_2\).
- Students annotate energy model: battery raises potential, resistors drop potential, not current.
- Re-attempt past-paper Q; error rate falls from 4/6 to 1/6.
4 Embedding the fixes — a one-week micro-plan
| Day | Habit (≤ 10 min) | Tool |
| Mon | Re-draw today's worksheet, highlighting sign conventions in colour. | Traffic-light margin from Developing IP-Level Problem-Solving Habits. |
| Tue | Voice-record a 60-s explanation of misconception #3. | Retrieval roulette. |
| Wed | Build a two-row error log: misconception, fix. | Google Sheet. |
| Thu | Quiz a classmate on misconception flashcards. | Anki deck. |
| Fri | Attempt one school past-paper Q; circle any myth that tempts you. | Paper autopsy method. |
5 Parent & tutor take-aways
- Spot the language — phrases like "uses up current" or "negative distance is wrong" flag hidden errors.
- Model uncertainty discipline — show rounding only at final lines; kids copy what they see.
- Use counter-examples — one quick demo outweighs ten slides of theory.
- Interleave — weave these myths into every topic so corrections stick.
6 Further reading
One-sentence takeaway
Misconceptions aren't random mistakes — they're sticky exit routes the brain takes under time-pressure; confront them early, and every future topic clicks faster.
