Calculation questions account for approximately 40% of the marks in IGCSE Physics. Fluency in calculations comes from structured practice, not from reading worked examples.
The calculation skill ladder
Level 1: Substitute and solve
You are given the equation and the values. Just plug in and calculate. Example: F = ma. m = 5 kg, a = 3 m/s^2. F = ?
Level 2: Choose the equation
You are NOT given the equation. You must identify which equation to use from the situation. Example: “A 5 kg mass accelerates at 3 m/s^2. Calculate the force.”
Level 3: Rearrange the equation
You need to rearrange the equation before substituting. Example: “A force of 15 N accelerates a mass at 3 m/s^2. Calculate the mass.”
Level 4: Multi-step problems
You need to use the answer from one calculation in another. Example: “A 2 kg ball falls from a height of 10 m. Calculate its speed when it hits the ground.” (Use GPE = mgh, then KE = 0.5mv^2, equate and solve for v.)
Level 5: Data interpretation + calculation
You read values from a graph or table, then calculate. Example: “Using the V-I graph, determine the resistance of the component.”
How to practise each level
Level 1 practice (beginners)
Write out 5 to 10 equations. For each, practise substituting different values. Use formula triangles if helpful. Repeat until substitution is automatic (no thinking required).
Level 2 practice
Take a list of past paper questions. Before solving, write which equation you would use and why. Then solve.
Level 3 practice
For each major equation, practise rearranging to find each variable. Do this on paper, not in your head. Repeat until you can rearrange any equation in under 30 seconds.
Level 4 practice
Work through multi-step problems from past papers. The key skill is linking two equations through a shared variable (e.g. GPE gives you energy, which equals KE, and you solve for speed).
Level 5 practice
Use Paper 6 and Paper 4 past papers that include data tables and graphs. Practise reading values accurately (check the scale, check the units) before calculating.
Practice schedule
| Week | Focus | Questions per day |
|---|---|---|
| Week 1 | Levels 1 and 2 | 10 questions |
| Week 2 | Levels 2 and 3 | 8 questions |
| Week 3 | Levels 3 and 4 | 6 questions (longer problems) |
| Week 4 | Levels 4 and 5 | 4 to 5 questions (full exam style) |
The three most important habits
- Write the equation first. Every time. Even if you can see the answer. The equation mark is a free mark.
- Show substitution with units. This earns a method mark and catches unit errors.
- Check your answer makes sense. If a person’s mass comes out as 0.5 kg or a car’s speed is 50 000 m/s, something is wrong.
Apply this study skill next
Need a Plan Based on Actual Work?
A private taught trial can help distinguish whether the repeated difficulty is mainly Physics knowledge, Mathematics, practical reasoning or exam technique before regular lessons are discussed.