To decide whether a relationship belongs in your tier, look it up in the current syllabus, note how it is labelled for Core or Extended, and check how equations are presented in specimen papers. Do this once per equation, and record the result.
This is the last lesson in physical reasoning in mixed tasks. It protects revision time, because Combined Science 0653 covers three sciences and you cannot afford to polish content you will not be asked. Always confirm facts on the Cambridge subject page for your exam year.
Why does the tier matter?
Combined Science 0653 is a single-award course with a Core and an Extended route. The syllabus lists what each route covers, and your exam centre enters you for one of them.
A relationship that is essential on one route may be absent on the other. A classmate’s notes, a textbook or a video may belong to a different route or a different syllabus year.
What is the routine, step by step?
- Write the relationship exactly as you meet it, with its symbols and units.
- Find the matching learning objective in your syllabus and note whether it is marked for Core, Extended or both.
- Check specimen papers for how it appears: given in the question, supplied on a data sheet, or expected from memory.
- Label it in your own notes: learn, recognise, or not needed.
- Confirm your tier with your teacher or exam centre if there is any doubt.
Worked example
A student keeps a list of relationships from mixed sources: speed = distance ÷ time, power = current × potential difference, pressure = force ÷ area. She wants to practise the speed relationship on this question: “A cyclist travels 120 m in 15 s. Calculate the average speed.”
Step 1, write it: speed = distance ÷ time, in m/s when distance is in metres and time in seconds.
Step 2, syllabus check: she finds the learning objective for speed in her syllabus and notes that it is marked for her route. (This is the step where each reader uses their own syllabus.)
Step 3, calculate: speed = 120 ÷ 15 = 8.0 m/s.
Step 4, check the unit: 120 m ÷ 15 s gives metres per second. 8.0 m/s × 15 s = 120 m, which matches the distance.
Step 5, label: she writes “learn” next to the relationship, and a different label for any item that the syllabus does not mark for her route.
What mistake should I watch for?
A common slip is to assume a relationship is needed because another student’s notes include it.
Mistaken working: “My friend learns this, so it must be on my paper.”
Friends may sit a different route, or follow a different syllabus year. The syllabus for your own exam year decides.
The correction is simple: check the syllabus first, then spend time practising. A second slip is to mix units, such as using km/h in a calculation that expects m/s.
Check yourself
Work these out, then open each answer.
1. A walker covers 2.4 km in 20 min. Find the average speed in m/s.
Show answer
Distance = 2.4 × 1000 = 2400 m. Time = 20 × 60 = 1200 s. Speed = 2400 ÷ 1200 = 2.0 m/s.
2. Change 90 km/h to m/s.
Show answer
90 km/h = 90 000 m per 3600 s = 90 000 ÷ 3600 = 25 m/s.
3. You find an equation in a video that you cannot locate in your syllabus. What are your next two steps?
Show answer
Search the syllabus learning objectives again using related terms, then ask your teacher or exam centre whether it applies to your route. Until confirmed, label it “not needed yet” rather than spending long on it.
Where this leads next
Put the routine to use in the physical reasoning practice set, and keep the scientific investigation critic nearby for questions about method. For help sorting your whole revision list by route, read about online one-to-one Combined Science tuition.