Resolving force Simulation
Resolving forces — teacher note
Spec. AQA 4.5.1.4 Resultant forces, the resolution statements. Higher tier only, and on both Physics (8463) and Combined Science: Trilogy (8464). Scale drawings only, so there is no trigonometry anywhere in it.
The one idea. A cart is pulled by a rope at an angle. That single pull can be replaced by two forces at right angles: a forward part that drags the cart along, and an upward part that lifts and moves it nowhere.
Three cases, in this order:
| pull | forward | up | |
|---|---|---|---|
| 1 | 5 N at 37° | 4 N | 3 N |
| 2 | 5 N at 53° | 3 N | 4 N |
| 3 | 10 N at 37° | 8 N | 6 N |
Case 2 is the lesson. Same pull as case 1, and the cart visibly gets less far, because more of the pull went into lifting. All three are 3‑4‑5 or 6‑8‑10, so every component is a whole number of squares.
What a pupil does. Three steps per case, then a summary.
- Show the pull — the rope goes taut and one red arrow appears along it.
- Split it up — the question: how much of the pull drags the cart forward? Two options only.
- Watch — the cart accelerates, driven by the forward part alone.
Then Your turn: they set the pull (1 to 10 N) and the rope angle themselves. At 0° the whole pull drags; at 90° none of it does and the cart never moves.
The support is a squared grid, which is the scale drawing the spec asks for. One square is one newton, and the answer is counted along the bottom. The dotted construction lines come out automatically on the first wrong answer rather than waiting for someone to find a button called Help me.
The wrong answer is diagnostic. It is always the other component, so a wrong tap tells you the pupil read the wrong side of the triangle rather than that they guessed.
Adaptation. The dial in the top bar switches the numbers between 1 to 10, tens and hundreds. Identical physics, identical picture, identical answer shape; only the arithmetic demand moves, so a class can work on one idea at three levels without anyone being handed a different task.
The Adapt menu carries read aloud, reading ruler, wider spacing, text size, Irlen overlays, colour vision filters, dark navy, projector mode, shape codes, reduce motion and slow it down. Three options are worth knowing about specifically: always show the dotted lines, show the square count, and skip the question, which fills in both parts so the lesson can stay on watching the cart.
Language. Plain words lead throughout — forward part, upward part. The exam vocabulary (components, horizontal and vertical component, resolving) is surfaced once, in a marked box on the summary screen.
Two misconceptions it targets directly. Reading the wrong leg of the triangle, and thinking the two components are extra forces added to the pull rather than a replacement for it.
Deliberately not included: friction, weight, the normal contact force, F = ma, and equilibrium. The summary is honest that a real path has friction and that the upward part changes how hard the cart presses down.
Practicalities. Single HTML file, opens in any browser, roughly 10 to 15 minutes for the three cases plus summary with Your turn open-ended afterwards. It pulls Three.js and the Lexend font from the internet on first load, so it needs a connection unless you cache it.