Why Problem Solving Is the Core Skill
IB Physics is not a memory test. The questions you’ll face in the exam will look different from anything you’ve practised. What the IB tests is your ability to apply physics principles to novel situations.
The good news: problem solving is a learnable skill. It follows patterns, and with deliberate practice, you can dramatically improve your speed and accuracy.
The 5-Step Framework
Step 1: Identify What’s Given and What’s Asked
Before touching your calculator:
- List all given quantities with their symbols, values, and units
- Identify the unknown you need to find
- Draw a diagram — even a rough sketch clarifies the physics
This takes 30 seconds and prevents the most common error: solving for the wrong variable.
Step 2: Select the Relevant Principle
Ask yourself: “What area of physics is this?”
- Motion → kinematics equations or Newton’s laws
- Energy → conservation of energy
- Collisions → conservation of momentum
- Circular motion → centripetal acceleration
- Fields → field strength and potential equations
- Waves → wave equation, interference, Doppler
If two principles could work, choose the one that directly connects your given quantities to the unknown.
Step 3: Write the Equation
Write the equation symbolically before substituting numbers. This:
- Earns you a method mark even if your answer is wrong
- Makes it easier to rearrange
- Prevents unit errors
Step 4: Substitute and Solve
- Convert all values to SI units before substituting
- Rearrange the equation before substituting if possible
- Keep intermediate values to at least 4 significant figures to avoid rounding errors
Step 5: Check Your Answer
Ask three questions:
- Are the units correct? If you calculated a speed and got kg, something is wrong
- Is the magnitude reasonable? A car speed of 3 × 10⁸ m/s is clearly wrong
- Does the sign make sense? Negative energy in a bound system is expected; negative temperature is not
Dimensional Analysis: Your Secret Weapon
If you’re stuck, check whether your equation is dimensionally consistent:
Example: Is v = √(2gh) correct?
- Left side: [v] = m/s = m·s⁻¹
- Right side: [2gh] = m·s⁻² × m = m²·s⁻²
- √[m²·s⁻²] = m·s⁻¹ ✓
This technique can help you:
- Verify equations you’re unsure about
- Eliminate wrong options in MCQs
- Reconstruct forgotten formulas
Tackling “Unfamiliar Context” Questions
The IB deliberately writes questions about contexts you haven’t studied. Don’t panic — the physics is always from the syllabus.
Strategy:
- Read the full question including any introductory text. The context sets up the physics.
- Identify the physics keywords: force, energy, field, wave, charge, current. These tell you which topic is being tested.
- Ignore the unfamiliar parts. If the question is about a “magnetohydrodynamic generator,” focus on the physics words: “magnetic,” “field,” “force on moving charges.”
- Draw on the data provided. The question will give you everything you need.
Common Problem Types and Approaches
”Two-step” Problems
The answer to part (a) is needed for part (b). If you can’t solve (a), assign a variable and continue — you may still earn method marks.
”Prove” or “Show that” Problems
Work forward from first principles. Never work backward from the given answer.
”Estimate” Problems
State your assumptions explicitly. Reasonable assumptions earn marks. The exact answer matters less than your logical approach.
”Compare” Problems
Structure: “A is [greater/less/equal] because [physics reason], while B is [different] because [contrasting physics reason].”
Deliberate Practice Protocol
Not all practice is equal. To improve problem solving:
- Attempt the problem for 5–10 minutes without looking at the solution
- If stuck, identify the gap — is it conceptual or mathematical?
- Read the solution, then close it and redo the problem from scratch
- Revisit the same problem 3 days later. If you can’t solve it again, you didn’t learn it
- Categorise your errors: calculation mistake? Wrong equation? Misread question?
Track your error types over time. Most students find that 60–70% of their errors fall into just 2–3 categories.
The Problem Solver’s Mindset
- “I don’t know how to start” → Draw a diagram and list the given quantities
- “The question is too hard” → Break it into sub-problems. Solve one step at a time
- “I keep making calculation errors” → Write more neatly, one step per line, and check units at each step
- “I understand the solution but couldn’t get it myself” → You need more practice with similar problems, not more theory