11 mark
What are the units of the moment of a force?
N m–1
N m
N s
N kg–1
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Moments (AQA A Level Physics)
Exam Questions
3 hours44 questions
21 mark
Which of the statements about the required conditions for equilibrium is correct?
The sum of the clockwise moments about a point equals the sum of the anticlockwise moments about the same point
There is no resultant force
1
2
1 & 2
neither
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31 mark
What is the centre of mass 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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41 mark
The diagram below shows a beam in equilibrium.
Which statement about the force at X is correct?
It is smaller than 100 N
It is also 100 N
It is larger than 100 N
Not enough information to know
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51 mark
The beam in the diagram below is in equilibrium by the three forces, X, 10.1 and 3.2 N.
What is the value of the force X?
2.9 N
3.2 N
6.9 N
13.3 N
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61 mark
A pair of scissors requires 10 N of force on each handle in order to close the blades.
What force is applied by the scissor blades in the diagram below to cause the blades to come closer together?
10 N
20 N
40 N
100 N
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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?
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81 mark
Which of the following statements about the pair of forces on a couple is correct?
| Magnitude | Direction | Parallel or Perpendicular |
A | Equal in magnitude | Opposite in direction | Parallel to the distance between them |
B | Equal in magnitude | Opposite in direction | Perpendicular to the distance between them |
C | Opposite in magnitude | Equal in direction | Parallel to the distance between them |
D | Equal in magnitude | Equal in direction | Perpendicular to the distance between them |
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91 mark
A steering wheel of diameter 0.38 m is rotated to the left by two forces of 2 N, as show in the diagram.
What is the moment of the couple produced by the rotation of the steering wheel?
0.38 N
0.50 N
0.76 N
1.0 N
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101 mark
A bird of mass 15 g sits on a uniform rod of mass 0.5 kg suspended from vertical wires with tension T1 and T2. T1 is 3 N and T2 is 2 N.
What is the total clockwise moment about point P?
0.053 N
1.0 N
1.2 N
1.3 N
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11 mark
A force of 9.8 N is applied at one end of a uniform beam of mass 2 kg that balances in equilibrium.
Which of the following corresponds to the correct value of the reaction R on the beam?
9.8 N down
9.8 N up
26 N down
26 N up
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21 mark
A load L of 5000 N is placed on a horizontal beam between two boxes A and B. The beam itself exerts a force of 10 kN at its centre of mass.
The two reaction forces from the boxes are R1 and R2.
Which of the following corresponds to the correct value of R1?
900 N
6000 N
9000 N
16 500 N
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31 mark
The uniform bar of length 0.60 m has a weight of 12 N and is in equilibrium in the diagram below. There is a hinge on the far right of the bar.
What is the reading on the Newtonmeter?
7 N
9 N
15 N
96 N
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41 mark
The wall hook shown has a weight of 50 N attached to the end.
What is the moment on the point of attachment to the base?
1 N m
1.25 N m
2.5 N m
5 N m
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51 mark
A door handle in the diagram below has a length 10 cm requires a force of 20 N to turn it.
If the handle breaks and the door must be opened using the axle of the handle, with a diameter of 0.5 cm, how much force is needed?
4 N
8 N
40 N
400 N
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61 mark
A load L is placed on a horizontal beam balanced by boxes A and B. The beam has a mass mg.
If load L is moved from box A towards box B, which of the following statements is true?
R1 increases and R2 decreases
R1 decreases and R2 increases
R1 = R2 throughout
Cannot tell without further data
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71 mark
A car bonnet, represented by QP, of mass 12 kg is pivoted at P. Its weight acts at G where QG = GP = 2.0 m.
What force, F, acting perpendicular to QP as shown, is required to hold the bonnet at 40° to the horizontal?
45 N
59 N
21 N
120 N
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81 mark
A car wheel nut can be loosened by applying a force of 310 N on the end of a bar of length 0.7 m as in X. A car mechanic is capable of applying forces of 650 N simultaneously in opposite directions on the ends of a wheel wrench as in Y.
What is the minimum length l of the wrench which would be needed for him to loosen the nut?
0.17 m
0.33 m
3.00 m
6.00 m
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91 mark
The diagram shows a uniform beam of weight 2.5 N and length of 150 cm is pivoted 32 cm from one end for use as a simple balance.
A rock is placed at the end of the beam. The beam moves to a steady horizontal position when a weight of 7.1 N is added at a distance of 80 cm from the pivot as shown.
What is the weight of the rock?
0.042 N
18 N
21 N
24 N
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101 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 incorrect?
it is in equilibrium because it is falling steadily
it is in equilibrium because the masses are equal
it is in equilibrium because it is the clockwise and anticlockwise moments are equal
it is in equilibrium because it has a resultant force
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11 mark
The diagram shows a uniform shelf along the axis XY with a mass 0.5 kg. A 3 kg load is placed at Y and a wire of tension T holds the shelf to the wall.
What is the magnitude of the tension in the supporting wire?
0.898 N
10.4 N
102 N
280 N
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21 mark
The wedge shown in the diagram below is suspended in equilibrium by a cable at an angle of 120º to the longest part.
The wedge has a mass of 200 kg, with a centre of mass ¾ of the length of AB from the hinge at A. AB is 2 m long and BC is 1.2 m high.
What is the tension on the cable?
2900 N
1700 N
990 N
1500 N
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31 mark
The medieval war machine shown below launches a stone projectile when the cable is released.
What is the tension T in the cable in the position shown?
2600 N
3100 N
3700 N
800 N
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41 mark
The diagram below represents the arm of a crane lifting a 100 kN load. The arm has a mass of 8000 kg and a machine produces a reaction force F of 5 m from the bottom of the arm. The crane arm is uniform and in equilibrium.
What is the value of F?
54 MN
52 MN
2.9 kN
2.9 MN
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51 mark
The diagram below shows an irregular object supported on two springs. The spring on the left has a spring constant of k1 and a load of 20 N acts 0.50 m from this spring and 0.25 m from the spring on the right.
When the object is placed on the bottom of the springs, they each extend by the same amount.
If the object is to be horizontal, what is the value of the spring constant for the spring on the right?
0.5 k1
5 k1
2 k1
k1
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61 mark
A triangular object with a base diameter of 1m below is to be tilted until it falls over. The arrow drawn is the point at which the centre of mass of the cone acts.
What height will the highest point on the base be just before the object falls over?
34 cm
91 cm
64 cm
94 cm
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71 mark
A car is driving up a uniform beam, of length 12 m. The car has a mass of 1000 kg and the beam has a mass of 200 kg.
How far along the beam beyond the pivot point can the car go just before the beam topples?
0.4 m
0.6 m
0.8 m
1.0 m
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81 mark
The diagram shows a child’s balancing game.
The wooden rod is uniform and all the rings are of equal mass. Two rings are hung on peg 14, one on peg 2 and one on peg 11.
On which hook must a fourth ring be hung in order to balance the rod?
2
7
5
4
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91 mark
A uniform rod with a rubber handle and wooden section is made to balance on a pivot as shown below.
What is the ratio 
?
3.1
5.9
6.1
9.6
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101 mark
The diagram below four tangential forces applies to a circular object with radius r.
If the clockwise direction is taken as positive, what is the resultant moment acting on the object?
64 r clockwise
0 stationary
12 r clockwise
12 r anticlockwise
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