Calculation skills
This lesson builds equation selection, rearranging and unit conversion for GCSE Physics.
Use the core lesson first, then match the exam-board guidance to your school route. Many pupils meet this content through Combined Science as well as Separate Physics.
What you will learn
Exam-board fit
Exact paper labels and specification-point numbering vary by board and cohort, so match this lesson to your school route before using past-paper questions.
Equation practice set supplied on this page
Use the mixed equation prompts to practise identifying quantities first, then substituting values with units.
Clear explanation
The safest calculation routine is: identify the quantity asked for, write down the known values, choose the equation, rearrange if needed, substitute with units, calculate and check the answer.
Unit conversion matters because GCSE Physics equations usually expect standard units. For example, 2.5 kJ is 2500 J, 30 cm is 0.30 m and 4 minutes is 240 s.
If an answer looks impossible, check powers of ten, whether you used seconds rather than minutes, and whether the equation was rearranged the right way round.
Worked examples
Convert before calculating
A device transfers 3.6 kJ in 2 minutes.
Convert 3.6 kJ to 3600 J and 2 minutes to 120 s.
power = energy transferred ÷ time = 3600 ÷ 120
Quick checks
Choose an answer, then check your thinking.
1. What should you do before substituting values into an equation?
2. What is 0.45 kJ in joules?
Practice questions
Question 1
Convert 75 cm into metres.
Reveal answer and marking guidance
Answer: 0.75 m.
Marking: Credit dividing by 100.
Question 2
A motor transfers 4800 J in 60 s. Calculate power.
Reveal answer and marking guidance
Answer: 80 W.
Marking: Credit power = energy ÷ time and 4800 ÷ 60 = 80 W.
Question 3
Rearrange speed = distance ÷ time to make distance the subject.
Reveal answer and marking guidance
Answer: distance = speed x time.
Marking: Credit multiplying both sides by time.
Question 4
A student gets a car speed of 4000 m/s in a school problem. What should they do?
Reveal answer and marking guidance
Answer: Check units, substitution and equation choice because the answer is not sensible for a normal car.
Marking: Credit reasonableness check and a specific likely error such as minutes not seconds.
Exam practice ladder
Answers and marking guidance
The exact practice answers are hidden under each question so you can try first. For this lesson, marks come from using the correct physics model, choosing the right equation where needed, keeping units with values, and explaining changes with precise words such as transfer, resultant force, acceleration, evidence and uncertainty.
Common mistakes
- Using minutes when the equation needs seconds.
- Forgetting to convert centimetres to metres.
- Rearranging by guessing rather than doing the same operation to both sides.
- Writing a number without the final unit.
Exam-board guidance
All supported routes assess the core physics idea, but they may group topics, practicals and paper wording differently.
AQA GCSE Physics
AQA GCSE Physics: use this lesson for equation selection, rearranging and unit conversion, then check whether your class is taking Separate Physics or Combined Science.
OCR GCSE Physics
OCR GCSE Physics: the core physics idea is shared, but Gateway and Twenty First Century may organise questions differently.
Pearson Edexcel GCSE Physics
Pearson Edexcel GCSE Physics: practise the concept, the equation use and the practical language because questions often connect them.
Eduqas GCSE Physics
Eduqas GCSE Physics: learn the core explanation and practise applying it to unfamiliar contexts, data and practical questions.
WJEC Wales
WJEC Wales: check whether your class is using the current GCSE Physics route or a newer science route, then use this lesson for the shared physics idea.
CCEA GCSE Physics
CCEA GCSE Physics: connect the idea to your unit and remember that practical skills are assessed directly.
Extension challenge
Create a three-column table for five equations: quantity asked for, values given, and final unit.
Reveal answer
Example answer: A strong extension response names the physics model, uses accurate units and explains why the evidence supports the conclusion.
Next lesson
Next, continue with Circuit Calculations.