K323 / 2027

Chapter 4

Turning effects of forces

A force can make an object turn.

Spaced review

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  1. Moments and perpendicular distance

    Identify the pivot and force line, then calculate the turning effect and its direction.

  2. Balancing moments

    Include all the forces when applying the principle of moments, including the object's own weight.

  3. Centre of gravity

    Represent an object's weight at one point and locate that point using suspension lines.

  4. Stability and toppling

    Use the weight's line of action to explain the effects of centre-of-gravity height and base width.

Syllabus coverage

This chapter covers Turning effects of forces, topic 4(a-f), in the K323 syllabus (2027) and 6091 (2026).

Learn to choose the perpendicular distance, account for each turning effect and explain how an object balances.

Includes moments, equilibrium, centre of gravity and stability.

View the learning outcomes
4(a)
Describe a force's turning effect about a pivot and relate it to everyday examples. Moments and perpendicular distance
4(b)
Apply moment = force x perpendicular distance to new situations. Moments and perpendicular distance
4(c)
State the principle of moments for a body in equilibrium. Balancing moments
4(d)
Apply the principle of moments to new situations. Balancing moments
4(e)
Represent the weight of a body as acting at its centre of gravity. Centre of gravity
4(f)
Explain qualitatively how centre-of-gravity position affects stability. Stability and toppling