Forces and Motion
Forces and motion is the unit where physics stops being abstract and starts being the ramp, the toy car, the stopwatch. Almost every exam question here gives you a table or a graph from an actual experiment and asks you to read it correctly — identify a variable, describe a trend, calculate a speed. The marks are lost not because the physics is hard, but because students rush the reasoning: picking the wrong arrow for friction, averaging a graph instead of reading its gradient, or saying 'balanced forces' when they mean 'no forces'. This chapter fixes exactly those habits.
Overview — How This Chapter Fits Together
A force is a push or a pull. Nothing in this chapter is more complicated than that — the whole unit is about (1) naming which forces are acting, (2) working out whether they cancel out or not, and (3) using that to predict or explain how something moves. Motion itself is described using distance-time graphs and the quantities speed, velocity and acceleration. Friction and drag are the forces you meet in almost every real experiment, because they're the ones that make things slow down and stop.
- Every question in this topic reduces to one of three moves: name the force, read the graph, or compare the data across surfaces/conditions.
- Friction and drag are opposing forces — they always act against the direction of motion (or attempted motion), never with it.
- Balanced forces don't mean 'nothing is happening' — a skydiver at terminal velocity has balanced forces and is still falling at 55 m/s.
The shape of the chapter
Command terms that appear in this topic's questions
| Command term | What it demands | AO | Mark-earning move |
|---|---|---|---|
| Identify | Give a short, specific answer picked from the data/diagram — a name, a letter, a value. No explanation needed unless marks say so. | Criterion A | 1 mark for the correct item only — writing a full sentence when 'Identify' is asked wastes time, not marks, but reasoning without the actual answer named loses the mark. |
| Describe | State what happens, including the trend or pattern — not just one data point. | Criterion A/C | Needs a direction of change (e.g. 'distance decreases as roughness increases'), not just 'friction affects distance'. |
| Compare | Give a similarity AND a difference, or set two things side by side explicitly. | Criterion C | A description of only one surface/case, with no explicit contrast to the other, scores zero on a Compare question. |
| Explain | Give a reason — link cause to effect using a physics idea (e.g. friction, gravity). | Criterion A | A restated observation with no 'because' link earns no marks — examiners look for the causal word. |
| Calculate | Show the formula/working, substitute numbers, give a final answer with correct unit. | Criterion A | A correct numerical answer with no unit typically loses the final mark even if the number is right. |
Key point
Overview