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Question 1
This question is about moments. |
a) | State the equation linking moment, force and perpendicular distance.
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b) | The image below shows a uniform beam hinged on the wall and supported by force X. Calculate the distance from the hinge to centre of mass of the beam.
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c) | Calculate the clockwise moment due to the weight of the beam.
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d) | Explain what is meant by the principle of moments.
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e) | Calculate the value force X must have to keep the beam in equillibrium.
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Question 2
a) | A student constructs a diving board from a plank of wood and supports it at one end and in the centre. The length of the beam is 2.5 m and it has a mass of 20 kg. Calculate the weight of the beam. The gravitational field strength on earth is 9.8 N/kg.
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b) | The student climbs on the board at the centre and walks towards the right hand end. Describe how the clockwise moment due to the weight of the student varies as the student walks along the board.
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c) | A student of weight 500 N stands on the right hand end of the diving board. The student places a mass 50 cm from the left hand end of the board to prevent it toppling. Calculate the unknown mass required to prevent the board toppling.
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Question 3
A decorator stands on a beam supported by two wooden blocks. The weight of the beam is 120 N and the weight of the painter is 500 N. In the position shown, the support force at A is 100 N. |
a) | Calculate the support force at B.
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b) | Describe how the support forces vary as the painter walks to the left.
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c) | The painter is now 1 m from B. The total length of the beam is 2.5 m. Calculate the support forces A and B.
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Question 4
A student is trying to balance a playing card on the corner of the card. |
a) | Name the point labelled X.
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b) | The card has a mass of 2 g. Calculate the weight of the card. You may assume the gravitational field strength on Earth is 9.8 N/kg.
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c) | Calculate the clockwise moment due to the weight of the card.
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d) | State the principle of moments.
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e) | Calculate the horizontal force the student needs to apply to keep the card in equilibrium.
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Question 5
a) | Two students are sat on a see-saw. Student B has a mass of 60 kg. Calculate the weight of student B. You may assume the gravitational field strength on Earth is 9.8 N/kg.
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b) | Name point X.
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c) | State the principle of moments.
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d) | Calculate the resultant moment for the students on the see-saw.
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e) | Calculate the distance from X that student B should sit for the see-saw to be in equilibrium.
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Question 6
A 1 m ruler is supported at one end by a hinge and by a newton-metre 10cm from the other end. The student suspends 200 g from the ruler at 30 cm from the right hand end. The metre ruler has a mass of 125 g and can be assumed to be uniform. |
a) | Calculate the reading on the newton-metre.
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b) | Describe what happens to the reading on the newton-metre as the 200 g mass is moved to the left.
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Question 7
This question is about moments. Simon is pulling a 26 kg suitcase along the ground. |
a) | Calculate the weight of the suitcase. The gravitational field strength on earth is 9.8 N/kg.
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b) | Calculate the upwards force that Simon needs to apply to keep the suitcase in equilibrium.
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c) | Simon says increasing the length of the handle would makes it easier to keep the suitcase in equilibrium. Assume the distance between the centre of mass and the pivot remains the same. Explain if Simon is correct.
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Question 8
a) | The unit for moment is A kg m/s B N m C N D J
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b) | A force of 20 N acts at a perpendicular distance form a pivot of 2cm. Calculate the moment of the force. A 40 N m B 10 N m C 1,000 N m D 0.4 N m
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c) | Child A is 60 kg and child B is 55 kg. They sit on a see-saw. Child A sits 1.2m from the pivot and child B sits an unknown distance from the pivot. Calculate how far student B needs to sit for the see-saw to be balanced. A 1.31 m B 0.90 m C 1.1 m D 0.80 m
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Question 9
A student is investigating moments. A metre ruler is hinged at one end and supported by a newton-metre at the other end. The student's method is below:
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a) | State the independent variable in the student's investigation.
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b) | The student's results are in the table below. Plot a graph of distance against newton-metre reading. Model answer
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c) | Use data from the graph to estimate the newton-metre reading when the distance from the 300 g mass to the pivot was 45 cm.
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d) | State the principle of moments.
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e) | When there was no mass added to the metre ruler, there was still a reading of 0.05 N on the newton-metre. Explain why.
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f) | Calculate the weight of the ruler.
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