1a1 mark
Which of the following is a unit for the moment of a force?
N
N m
N/m
N/m2
1b1 mark
State the principle of moments.
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Moments (Edexcel IGCSE Physics)
Topic Questions
2a1 mark
A rubbish bin on wheels is tilted at different angles to see how far it can go without toppling over.
The weight of the bin acts through point X.
Which of these will topple?
2b1 mark
State the name of point X shown on the bin in (a).
2c1 mark
A person applies a force of 100 N to the bin to keep it stationary.
Which of the following is the correct calculation of the moment of the 100 N force?
100 N × 28 cm
100 N × 37 cm
100 N × 92 cm
100 N × 104 cm
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3a1 mark
State what is meant by a moment of a force.
3b1 mark
A uniform seesaw is in equilibrium with a box placed on each side.
The box on the left has an anticlockwise moment of 150 N m about the pivot.
The box on the right has weight W.
(i)
State the principle of moments.
(1)
(ii)
State the clockwise moment due to the box on the right.
(1)
3c2 marks
Show that the weight W of the box on the right side of the seesaw is 100 N.
3d2 marks
The box on the left-hand side of the seesaw is now removed.
State and explain what happens to the seesaw.
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4a1 mark
The centre of gravity of an object is
The point in the exact middle of the object
The point through which the mass of an object acts
The point through which gravity acts
The point through which the weight of an object acts
4b1 mark
The diagram shows a sign hanging outside of a shop.
Draw an X on the sign at its centre of gravity.
4c1 mark
One force which acts on the sign is its weight.
Complete the following sentence
| a balancing an accelerating a turning |
The moment of the weight produces .................................... effect.
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5a1 mark
The diagram shows a person beginning to lift the end of a heavy wooden pole.
As the pole is lifted, what is the size and direction of the moment produced by the weight of the wooden pole?
| moment | direction | |
| A. | 200 | clockwise |
| B. | 200 | anticlockwise |
| C. | 1250 | clockwise |
| D. | 1250 | anticlockwise |
5b2 marks
Complete the following sentences
| larger than smaller than equal to |
(i)
The minimum force needed to lift the end of the pole will be .................................... the weight of the pole.
(1)
| lifting force weight further from closer to |
(ii)
This is because the .................................... is .................................... the axis of rotation than the .................................... .
(1)
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1a1 mark
A toy train is placed on the middle of a bridge on a model railway.
The weight of the train acts through its centre of gravity. Ignore the weight of the bridge.
Which row of the table shows the correct values for forces X and Y?
1b2 marks
Describe how force X would change if the train moved from P to Q.
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2a2 marks
A student wants to investigate the principle of moments. He connects a ruler to a stand with a pivot and hangs a 2 N weight from the 60 cm mark on the ruler. He uses a newtonmeter to hold the ruler horizontal.
The scale on the newtonmeter reads from 0 N to 10 N.
Describe how the student could check that the ruler is horizontal.
2b4 marks
(i)
State the equation linking moment, force and distance from the pivot.
(1)
(ii)
Calculate the moment of the 2 N weight.
State the unit.
(3)
moment = ............................................... unit = ...............................................
2c3 marks
The student holds the ruler horizontal with the forcemeter at the 10 cm mark. He expects the reading on the forcemeter to be 12 N. The actual reading is 10 N.
Explain why
(i)
The correct reading should be larger than 12 N.
(2)
(ii)
The actual reading is only 10 N.
(1)
2d3 marks
A picture in the student’s textbook shows two fishermen using a pole to carry some fish.
Fisherman A and fisherman B feel different forces on their shoulders.
Use ideas about moments to explain why fisherman A feels the larger force.
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3a2 marks
The diagram shows a gate with a lever-operated catch.
A loop on the bolt fits around the lever-arm at A.
(i)
Describe how the lever-arm is used to move the bolt.
(1)
(ii)
Suggest why the spring is needed.
(1)
3b6 marks
The lever arm operates using the principle of moments.
(i)
State the principle of moments.
(1)
(ii)
The force applied at point B is 22 N. The pivot is 110 cm from point B and 38 cm from point A.
Calculate the force exerted on the lever-arm at point A by the spring.
(3)
force at point A = ............................................... N
(iii)
Explain how the force applied at point B would need to change if the distance from the pivot to point A is increased.
(2)
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4a1 mark
A man uses a uniform plank to lift a block.
He holds the plank horizontal.
The arrows on the diagram represent three forces on the plank.
Complete the table to identify the missing force.
4b3 marks
(i)
State the equation linking moment, force and perpendicular distance from the pivot.
(1)
(ii)
Calculate the clockwise moment of the block about the pivot.
(2)
moment = ........................................ Nm
4c4 marks
Calculate the force of the man pushing down on the plank.
force = ........................................ N
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5a1 mark
A student investigates the vertical forces acting on the ends of a horizontal ruler when it supports a load.
The ruler hangs from two newtonmeters with a weight suspended from it as shown.
The student moves the weight along the ruler and records forces B and C by taking readings from the newtonmeters.
In this investigation, the independent variable is
Distance A
Force B
Force C
Force D
5b1 mark
In this investigation, the controlled variable is
Distance A
Force B
Force C
Force D
5c5 marks
The student records the following readings
She plots this graph to show how force C changes with distance A.
(i)
Complete the student's graph by labelling the vertical axis.
(1)
(ii)
Using the same grid and axes, plot a second line to show how force B varies with distance A.
(3)
(iii)
Use the lines on the graph to find distance A for which force B and force C are equal.
(1)
distance = ................. cm
5d1 mark
Suggest why neither force B nor force C are ever zero during the investigation.
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1a3 marks
Photograph C shows how a student can use a claw hammer to pull a nail from a piece of wood.
The mass of the hammer is 0.454 kg.
(i)
Calculate the weight of the hammer.
(2)
weight = ............................................... N
(ii)
From what point does this weight act?
(1)
1b4 marks
Photograph D shows the directions of two other forces on the hammer.
(i)
Draw an arrow on photograph D to show the force on the nail from the hammer.
(2)
(ii)
Suggest two ways that the student could increase the moment on the hammer.
(2)
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2a1 mark
A man uses a wheelbarrow to carry some logs along a flat path, as shown.
He pushes with a horizontal force of 140 N and the wheelbarrow moves 39 m.
The man stops and holds the wheelbarrow horizontally, as shown.
The man exerts a total upward force of FN. The weight of the loaded wheelbarrow is 470N.
Mark X on the diagram to indicate the centre of gravity of the loaded wheelbarrow.
2b5 marks
(i)
State the equation linking moment, force and perpendicular distance from the pivot.
(1)
(ii)
Calculate the force F.
(4)
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3a4 marks
The diagram shows the apparatus used to investigate moments.
The 2 N weight is placed 60 cm from the pivot.
The newtonmeter is placed 10 cm from the pivot.
(i)
State the equation linking moment, force and perpendicular distance from the pivot.
(1)
(ii)
Calculate the reading on the newtonmeter.
Ignore the weight of the ruler.
(3)
reading = ............................................... N
3b3 marks
The metre rule is replaced by an iron bar.
The iron bar is 1 m long and has a weight of 10 N.
The newtonmeter and the 2 N weight stay in their original position.
Explain how this change affects the reading on the newtonmeter.
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4a5 marks
A painter sets up a uniform plank so he can paint a wall.
The plank is 3 m long and weighs 500 N.
(i)
Use the principle of moments to show that the upward force A is 250 N.
(4)
(ii)
State the value of force B.
(1)
force B = ............................N
4b3 marks
The painter stands on the plank as shown.
(i)
Draw an arrow on the diagram to show the weight of the painter.
(1)
(ii)
Describe the changes in forces A and B when the painter stands on the plank.
(2)
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