CAIE IGCSE Physics 1.5.2 Turning Effect of Forces Topic Practice

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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

Question 1

[Maximum number: 3]

Question (a)

(a)

State what is meant by the moment of a force about a point.

[ 1 ]

Question (b)

(b)

Fig. 2.1 shows a large crane on a construction site lifting a block of mass 14000 kg .

Fig. 2.1

Fig. 2.1

Calculate the moment about A due to the 14000 kg block suspended from B.

moment =
[ 2 ]

Question 2

[Maximum number: 3]

A radio transmitter is a very tall, thin cylinder. It is prevented from falling over by wires which have one end fixed to the transmitter and the other end fixed in the ground. The ends of the wires in the ground are a long distance from the transmitter.

Fig. 4.1 shows the transmitter and two of the wires.

Fig. 4.1

Fig. 4.1

Wire W is under tension and it exerts a force T on the transmitter.

The force T produces a moment on the transmitter about its base.

Describe how the moment produced by T is calculated and indicate on Fig. 4.1 what is meant by any other terms in the description.

Question 3

[Maximum number: 4]

Fig. 3.1 shows two children balanced on a seesaw. A seesaw is a length of wood which rotates about a central pivot.

Fig. 3.1

Fig. 3.1

Question (a)

(a)

Child B moves 0.050 m further away from the pivot.

[ 4 ]

Question (i)

(i)

Explain why the seesaw rotates clockwise.

[ 1 ]

Question (ii)

(ii)

Child A puts on a backpack and the seesaw now balances.

Calculate the mass of the backpack.
mass = kg [3]

[ 3 ]

Question 4

[Maximum number: 1]

State what is meant by the moment of a force about a point.

Question 5

[Maximum number: 2]

Fig. 1.1 shows a helicopter which is stationary at a height of 1500 m above the ground.

Fig. 1.1 (not to scale)

Fig. 1.1 (not to scale)

State the two conditions necessary for the helicopter to remain in equilibrium. condition 1
condition 2

Question 6

[Maximum number: 3]

A rock climber, of total mass 62 kg , holds herself in horizontal equilibrium against a vertical cliff. She pulls on a rope that is fixed at the top of the cliff and presses her feet against the cliff.

Fig. 3.1 shows her position.

Fig. 3.1 (not to scale)

Fig. 3.1 (not to scale)

The climber's centre of mass is 0.90 m from the cliff.

The line of the rope meets the horizontal line through her centre of mass at a distance of 1.2 m from the cliff, as shown in Fig. 3.1. The rope is at an angle of 60∘60^{\circ} to the horizontal.

Determine the tension in the rope.
tension = [3]
[Total: 8]

Question 7

[Maximum number: 3]

Describe an experiment involving vertical forces to show that there is no net moment on an object in equilibrium. You may draw a diagram in the space provided.

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