K326 / K327 / 2027

Chapter 4

Dynamics

Forces explain how motion changes.

Learn to draw the forces on a chosen object, find their resultant and connect it to acceleration.

Includes balanced and unbalanced forces, free-body diagrams, interaction pairs, resultant force and friction. For K326 / K327 (2027) / 5086 / 5087 (2026).

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  1. Forces on one body

    Draw a free-body diagram and explain the effects of balanced and unbalanced forces.

  2. Pairs of forces

    Identify forces in an interaction pair and distinguish them from forces balancing on one body.

  3. Resultant force and acceleration

    Find the combined force before using F = ma, and explain how force and mass affect acceleration.

  4. Friction and motion

    Explain how friction can prevent sliding, slow a moving object or provide grip.