Relate, explain, link — the three verbs

Three verbs, in ascending order

There are three things a report can do with the physics, and everything about how you write depends on which one you are aiming at.

What the writing does	What that looks like
Relate the key physics ideas to the selected context	Name the physics that applies here, and say where in the context it applies
Explain how or why the key physics ideas relate to the context	Give the mechanism — the causal chain from the physics to the observed feature
Link key physics ideas together to give a coherent picture of the physics relevant to the context	Show how two or more ideas interact to produce the behaviour of the whole system

What "coherent picture" means

This is the phrase that carries the most weight, and it is often misread as "cover more topics".

• A coherent picture is one explanation in which the parts depend on each other, not several correct explanations placed side by side.
• Test your report with this question: if I deleted one of my physics ideas, would the rest still make sense on its own?
  • If yes, you have a list.
  • If no — if the second idea is needed to explain something the first leaves unexplained — you have a coherent picture.

What is being judged is the physics, not the context

• The depth of the physics decides how good the report is — not how fully or how fluently the context is described. A polished ten-page account of how a technology works, with two thin physics ideas in it, counts as two thin physics ideas.
• Describe only as much of the context as the physics needs to land. Every paragraph of description that no physics ever uses is a paragraph doing no work.
• Copying or closely paraphrasing a source shows nothing about your understanding, however well chosen the source is. Reproducing an explanation someone else wrote is evidence that you found it, not that you understood it.
• What does show understanding is physics you have processed yourself: a calculation using real values from the context, a diagram you drew of what is happening, an explanation built from your own measurements or observations. Reference your sources — it is good practice and it keeps the work verifiable — but the understanding is in what you did with them.

The step up from Level 2

At Level 2 you gave the physics relevant to a context. At Level 3 you give the application of physics to a context. In practice:

• The physics must be at curriculum Level 8 — the content of the Level 3 course. A context explained with nothing but Level 2 mechanics is not a Level 3 report, however well written.
• Quantitative application is expected where the context allows it. A calculation using real values from the context is the clearest evidence of application.
• The context can be technological, biological or astronomical — astronomy is available at Level 3 and is not at Level 2.

Choosing physics at the right level

Level 2 idea	Its Level 3 counterpart
Momentum in a straight line	Momentum in two dimensions; circular motion and centripetal force
Simple wave behaviour	Standing waves, resonance, beats, the Doppler effect
Ohm's law and simple circuits	AC circuits, reactance, phasors, RC time constants, induction
Energy transfer	Simple harmonic motion; energy in oscillating systems
Alpha, beta, gamma decay	Photons, energy levels, mass–energy, relativity

One important restriction

• The physics you use here must be different from the physics you use for your socio-scientific issue report. Both pieces of work apply physics outside the classroom, but they have to draw on different content.
• Plan the two together at the start of the year so you do not have to rewrite one of them.