CIE A Level Physics

Topic Questions

Syllabus Edition

First teaching 2020

Last exams 2024

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4.1 Forces: Turning Effects & Equilibrium

11 mark

What is the centre of gravity of an object?

  • the geometrical centre of the object

  • the point about which the total torque is zero

  • the point at which the weight of the object may be considered to act

  • the point through which gravity acts

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21 mark

The diagrams show the forces acting on different bodies.

 Which body cannot be in equilibrium?

cie-ial-physics-mcq-4-1-q2

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31 mark

A force of 5.0 N pushes a ball due north and another force of 12.0 N pushes it due east.

 What is the magnitude of the net force acting on the ball?

  • 7.0 N

  • 10.9 N

  • 13.0 N

  • 17.0 N

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41 mark

The diagram shows four forces applied to a circular object.

cie-ial-images153png

Which of the following describes the resultant force and resultant torque on the object?

 

Resultant force

Resultant torque

A

B

C

D

non-zero

non-zero

zero

zero

non-zero

zero

non-zero

zero

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51 mark

A street lamp is fixed to a wall by a metal rod and a cable.

cie-ial-physics-mcq-4-1-q5-diagram-1

Which vector triangle represents the forces acting at point P?

4-1-q5-diagram-2

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61 mark

A uniform metre rule of weight 4.0 N is pivoted at the 60 cm mark. A 6.0 N weight is suspended from one end, causing the rule to rotate about the pivot.

cie-ial-physics-mcq-4-1-q6

At the instant when the rule is horizontal, what is the resultant turning moment about the pivot?

 

Resultant moment

Direction

A

B

C

D

2.0 N m

2.0 N m

2.8 N m

2.8 N m

clockwise

anticlockwise

clockwise

anticlockwise

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71 mark

Two co-planar forces act on the rim of a wheel. The forces are equal in magnitude.

Which arrangement of forces provides only a couple?

cie-ial-physics-mcq-4-1-q7

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81 mark

The diagram shows a plan view of a door which requires a moment of 14 N m to open it.

cie-ial-physics-mcq-4-1-q8

What is the minimum force that must be applied at the door’s midpoint to ensure it opens?

  • 4.9 N

  • 9.8 N

  • 20 N

  • 40 N

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91 mark

Two parallel forces, each of magnitude F, act on a body as shown

cie-ial-physics-mcq-4-1-q9

What is the magnitude of the torque on the body produced by this couple?

  • Fd

  • Fs

  • 2 Fd

  • 2Fs

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101 mark

Forces of 3 N, 4 N and 5 N act at one point on an object. The angles at which the forces act can vary.

 What is the value of the minimum resultant force of these forces?

  • Zero

  • between 0 and 2 N

  • 2 N

  • between 2 N and 4 N 

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11 mark

The diagrams show two ways of hanging the same picture.

cie-ial-physics-mcq-4-1-q21-diagram-1

In both cases, a string is attached to the same points on the picture and looped symmetrically over a nail in a wall. The forces shown are those that act on the nail.

In diagram 1, the string loop is shorter than in diagram 2.

Which information about the magnitude of the forces is correct?

  • R1 = R2   T1 < T2

  • R1 = R2   T1 > T2

  • R1 > R2   T1 < T2

  • R1 < R2   T1 = T2

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21 mark

A uniform ladder rests against a vertical wall where there is negligible friction. The bottom of the ladder rests on rough ground where there is friction. The top of the ladder is at a height h above the ground and the foot of the ladder is at a distance 2a from the wall.

 The diagram shows the forces that act on the ladder.

cie-ial-physics-mcq-4-1-q22

Which equation is formed by taking moments?

  • Wa + Fh = 2Wa

  • Fa + Wa = Fh

  • Wa + 2Wa = Fh

  • Wa – 2Wa = 2Fh

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31 mark

An archer draws his bowstring back to position X. The bowstring and arrow are shown. The tension T in the string is also shown. Then he draws the bowstring back further to position Y.

cie-ial-physics-mcq-4-1-q23-diagram-1

The archer finds the resultant force on the arrow is greater when the arrow is released from position Y.

What is the increase in force?

  • 51 N

  • 55 N

  • 102 N 

  • 110 N

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41 mark

The diagram shows a solid cube with weight W and sides of length L. It is supported by a frictionless spindle that passes through the centres of two opposite vertical faces. One of these faces is shaded.

cie-ial-images191png

The spindle is now removed and replaced at a distance  begin mathsize 11px style L over 4 end style    to the right of its original position.

cie-ial-images192png

When viewing the shaded face, what is the torque of the couple that will now be needed to stop the cube from toppling?

  •   fraction numerator W L over denominator 2 end fraction anticlockwise

  • begin mathsize 12px style fraction numerator W L over denominator 2 end fraction end style   clockwise

  • fraction numerator W L over denominator 4 end fraction   anticlockwise

  •  begin mathsize 12px style fraction numerator W L over denominator 4 end fraction end style  clockwise

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51 mark

The diagram shows two fixed pins, Y and Z. A length of elastic is stretched between Y and Z and around pin X, which is attached to a trolley.

cie-ial-images194png

X is at the centre of the elastic and the trolley is to be propelled in the direction P at right angles to YZ. The tension in the elastic is 4 N.

 What is the force accelerating the trolley in the direction P when the trolley is released?

  • 2.4 N

  • 3.2 N

  • 4.8 N 

  • 6.4 N

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61 mark

The diagram shows a rope bridge that a student makes on an adventure training course. The student has a weight W.

cie-ial-images196png

Which formula gives the tension T in the rope?

  • T equals fraction numerator W over denominator 2 space cos space theta end fraction

  • T equals fraction numerator W over denominator 2 space sin space theta end fraction

  • T equals fraction numerator W over denominator cos space theta end fraction

  • T equals fraction numerator W over denominator sin space theta end fraction

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71 mark

A uniform beam is pivoted at P as shown. Weights of W and 2 W are attached to its ends. The beam is marked at x intervals. The weight of the beam is 10 W

 cie-ial-images198png

At which point should a 2 W weight be attached to achieve equilibrium?

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81 mark

A uniform metre rule of mass 100 g is supported by a pivot and a string as shown in the diagram. The beam is marked at 2 x intervals. The string passes round a frictionless pulley and carries a mass of 20 g.

cie-ial-images200png

At which mark on the rule must a 50 g mass be suspended so that the rule balances?

  • 0.4 x 

  • 3.6 x

  • 4.4 x

  • 6.4 x

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91 mark

A heavy uniform beam of length L is supported by two vertical cords as shown

cie-ial-images201png

What is the ratio of   T subscript 1 over T subscript 2  of the tensions in these cords?

  • 1 third

  • 1 half

  • 2 over 1

  • 3 over 1

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101 mark

A trailer of weight 30 kN is attached to a truck. The trailer is raised until it is held at 50˚ to the horizontal by a vertical force F as shown in the diagram.

The trailer is 2.7 m in length and the position of its centre of gravity G is a third of the length from the hinge at O.

cie-ial-images202png

What is the vertical force F applied to the end of the trailer?

  • 10 kN

  • 15 kN

  • 30 kN

  • 60 kN

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11 mark

A uniform metre rule is hung from the ceiling as shown

cie-ial-physics-mcq-4-1-q11

The rule balances when a 75 g mass is hung from one end of the ruler 

What is the mass of the metre rule?

  • 38 g

  • 51 g

  • 141 g

  • 159 g

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21 mark

Four beams of the same length each have three forces acting on them.

Which beam has both zero resultant force and zero resultant torque acting?

cie-ial-physics-mcq-4-1-q12

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31 mark

The diagram shows a child’s balancing game.

cie-ial-physics-mcq-4-1-q13

The wooden rod is uniform and all the rings are of equal mass. Two rings are hung on peg 14 and one on peg 2.

 On which hook must a fourth ring be hung in order to balance the rod?

  • 2

  • 3

  • 5

  • 6

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41 mark

An object, made from two equal masses joined by a light rod, falls with uniform speed through air. The rod remains horizontal.

 Which statement about this system is correct?

  • it is not in equilibrium because it is falling steadily

  • it is not in equilibrium because it is in motion

  • it is not in equilibrium because there is a resultant torque

  • it is in equilibrium because there is no resultant force and no resultant torque

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51 mark

A man holds a 200 N load stationary in his hand. The combined weight of the forearm and hand is 25 N. The forearm is held horizontal, as shown

cie-ial-physics-mcq-4-1-q15

What is the vertical force F needed in the biceps?

  • 1340 N

  • 1400 N

  • 1460 N

  • 1520 N

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61 mark

A 20 cm ruler is pivoted at its centre. Equal and opposite forces of magnitude 5.0 N are applied to the ends of the ruler, creating a couple as shown

cie-ial-physics-mcq-4-1-q16-diagram-1

What is the magnitude of the torque of the couple on the ruler when it is in the position shown?

  • 0.17 N m

  • 0.87 N m

  • 1.0 N m

  • 1.7 N m

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71 mark

A spindle is attached at one end to the centre of a lever of length 1.60 m and at its other end to the centre of a disc of radius 0.25 m. A string is wrapped round the disc, passes over a pulley and is attached to an 800 N weight.

cie-ial-physics-mcq-4-1-q17

What is the minimum force F, applied to each end of the lever, that could lift the weight?

  • 62.5 N

  • 125 N

  • 250 N

  • 750 N

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81 mark

A uniform beam of mass 1.2 kg is pivoted at P as shown. The beam has a length of 0.70 m and P is 0.40 m from one end. Loads of 5.0 kg and 7.0 kg are suspended 0.65 m and 0.35 m from the pivot as shown.

cie-ial-physics-mcq-4-1-q18

What torque must be applied to the beam in order to maintain it in equilibrium?

  • 0.62 N m

  • 0.98 N m

  • 6.1 N m

  • 9.6 N m

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91 mark

A rigid L-shaped lever arm is pivoted at point P.

cie-ial-physics-mcq-4-1-q19

Three forces act on the lever arm, as shown in the diagram.

 What is the magnitude of the resultant moment of these forces about point P?

  • 5 N m

  • 65 N m

  • 95 N m

  • 155 N m

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101 mark

A ladder is positioned on icy ground and is leant against a rough wall. At the instant of release, it begins to slide.

 Which diagram correctly shows the directions of the forces P, W and R acting on the ladder as it slides?

cie-ial-physics-mcq-4-1-q20

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