From a force diagram to an explanation — Bingkun Qi

About this project

Substituting into F = ma does not by itself show that a student knows which forces belong in the equation. This lesson starts with modelling: choose the object, draw the external forces acting on it, define a positive direction, then write and interpret the equation.

Short questions on constant velocity and third-law pairs lead into a worked crate example. Students then compare the forces before and after a rope is released, apply the model to a suspended load, and attempt an exit ticket independently. The teacher plan specifies when to model, when to step back, and how to use an error to revisit the relevant step.

Features and use cases

• An English worksheet with separate solutions: attempt first, check afterwards
• Original force diagrams that make the object, external forces and positive direction explicit
• A Chinese teacher plan with prompts, feedback cues and marking guidance
• Transfer from one model to a released rope, vertical motion and Newton’s third law

From a force diagram to an explanation

The learning goal

Identify the object, external forces and positive direction, then connect the diagram, equation and explanation.

The learning materials

An English worksheet, separate solutions and a Chinese teacher plan preserve the full classroom-practice sequence.

Feedback by design

Keep the first response, ask the student to explain a correction, then check transfer with a new exit-ticket situation.

Diagnose and keep the reasoning

Minutes 0–5 · Two short questions separate constant velocity from resultant force, and balanced forces from a third-law pair. Keep the first response as a starting point for feedback.

Make the force model explicit

Minutes 5–18 · Choose one object, identify its external forces and set a positive direction. A pulled crate connects the diagram, the equation and the direction of acceleration.

Transfer, explain and check

Minutes 18–45 · Students work independently on a released rope and a suspended load, explain a correction, then use a new exit-ticket situation to check transfer.

Materials have been prepared and checked; classroom trials are still pending. This is a teaching-design example, with no claim about measured student outcomes.

Lesson materials

Try the worksheet before opening the solutions. The teacher plan is in Chinese; the solutions include English model explanations. The worksheet’s last page references optional official homework; that examination paper is not included.

Student worksheet · English · 5 pages

Solutions & marking guidance · Chinese with English model explanations · 4 pages

Teacher plan · Chinese · 3 pages

Teaching tools & projects