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CAIE IGCSE Physics Turning Effect of Forces

Practise moments, perpendicular distances and equilibrium, balancing clockwise and anticlockwise effects and designing a metre-rule demonstration.

Syllabus
2026–2028
Course
Physics 0625

Exam points

  • calculate moment as force multiplied by perpendicular distance from the pivot
  • set total clockwise and anticlockwise moments equal and also check zero resultant force
  • describe a pivoted-ruler experiment with measured masses and distances on both sides

Covered syllabus points

1.5.2.1—Moment of a force as a measure of its1.5.2.2—Moment of a force as moment = force ×1.5.2.3—Apply the principle of moments to1.5.2.4—That, when there is no resultant force1.5.2.5—Apply the principle of moments to1.5.2.6—An experiment to demonstrate that

1.5.2 Turning effect of forces question 1

[Maximum number: 7]

Question (a)

(a)

Define the moment of a force and describe the effect that it measures.

[ 3 ]

Question (b)

(b)

A large rectangular block of stone has a square base of side 3.4 m . Fig. 3.1 shows the block at rest on a horizontal surface.

Fig. 3.1

Fig. 3.1

The block is of uniform density and the centre of gravity G is at its centre.

[ 2 ]

Question (i)

(i)

The weight of the block is 1.3×107 N1.3 \times 10^{7} \mathrm{~N}.

Calculate the moment of the weight of the block about corner X .
moment of weight =

[ 2 ]

Question (c)

(c)

The block shown in Fig. 3.1 is in equilibrium.

State the two different conditions that apply when an object is in equilibrium.
1
2

[ 2 ]

1.5.2 Turning effect of forces question 2

[Maximum number: 4]

Fig. 7.1 shows a barrier at the entrance to a car park. The wooden barrier arm has a weight of 60 N which acts through the centre of gravity at the position shown on Fig. 7.1.

Fig. 7.1

Fig. 7.1

Question (a)

(a)

Initially the wooden barrier arm is horizontal.

[ 4 ]

Question (i)

(i)

Using Fig. 7.1, calculate the clockwise moment of the weight of the wooden arm about the pivot.
clockwise moment = Nm [1]

[ 1 ]

Question (ii)

(ii)

The wooden barrier arm is in equilibrium. The mass of the soft iron bar A is 23 kg .

Calculate the distance d between the pivot and the joint holding the soft iron bar A .
distance d =

[ 3 ]
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