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1Name:T E S TS

3 Forces and pressureAnswer all questions and show your working out for maximum creditTime allowed : 30 minsTotal points available : 32

Core curriculum

1 A bicycle pump has its outlet sealed with a tight rubber bung, as shown in Fig. 1.1.

Fig. 1.1

a The temperature of the air in the pump is kept constant. The handle of the pump is pushed in so that the piston moves from A to B.

Tick the correct box in each row of the table below to show how each quantity varies as the piston is moved.

greater with piston at A

greater with piston at B

same with piston at A or B

the average speed of the air molecules

the frequency with which the air molecules hit the walls and the piston

the pressure of the air in the pump

[3]

b When the handle is pushed in even further, the rubber bung pops out of the hole. Which two forces are equal just before the bung pops out? Tick two boxes.

friction force between bung and hole

resultant due to forces of air on each side of piston

resultant due to forces of air on each side of bung

gravitational force on bung

force of air on walls

[2]

[Total: 5]

Cambridge IGCSE Physics 0625 Paper 2 Q6 November 2009

2 a Fig. 2.1 shows a uniform rod.

Fig. 2.1

i Use your rule to find the length of the rod.

length = ...........................................cm [1]

ii On Fig. 2.1, show the position of the centre of mass of the rod using the letter C.

[1]

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b Fig. 2.2 shows another rod, of the same length as the previous one, but this rod is thicker at one end.

Fig. 2.2

Use your judgement to mark with the letter M approximately where the centre of mass of this rod will be.

[2]

[Total: 4]

Cambridge IGCSE Physics 0625 Paper 2 Q1 June 2008

3 A beam is pivoted at its centre. Three forces, F1, F2 and F3, act on the beam as shown in Fig. 3.1.

Fig. 3.1

a Which of the forces exert(s)

a clockwise moment,

an anticlockwise moment? [3]

b When the beam is released, the right-hand side of the beam starts to go down. Which of the three distances, a, b or c, should be decreased in order to balance the beam? Explain your answer.

Which distance?

Explanation

[3]

c Fig. 3.2 represents a simple beam-balance with the pivot accurately at its centre.

Fig. 3.2

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The person using the beam-balance puts the object to be weighed in the left-hand pan. He has a selection of standard masses to put in the right-hand pan, but he finds he cannot exactly balance the beam.

His best attempts are

masses used effect

10 g, 10 g, 5 g, 2 g, 2 g beam tips down slightly on the left-hand side

20 g, 10 g beam tips down slightly on the right-hand side

Estimate the mass of the object.

mass = g [1]

[Total: 7]

Cambridge IGCSE Physics 0625 Paper 2 Q3 June 2008

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Extended curriculum

4 a A man squeezes a pin between his thumb and finger, as shown in Fig. 4.1.

Fig. 4.1

The finger exerts a force of 84 N on the pinhead.

The pinhead has an area of 6.0 × 10–5 m2.

i Calculate the pressure exerted by the finger on the pinhead.

pressure = [2]

ii State the value of the force exerted by the pin on the thumb.

[1]

iii Explain why the pin causes more pain in the man’s thumb than in his finger.

[2]

b The density of the water in a swimming pool is 1000 kg/m3. The pool is 3 m deep.

i Calculate the pressure of the water at the bottom of the pool.

pressure = [2]

ii Another pool has the same depth of water, but has twice the area.

State the pressure of the water at the bottom of this pool.

pressure = [1]

[Total: 8]

Cambridge IGCSE Physics 0625 Paper 3 Q6 June 2009

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5 A student investigated the stretching of a spring by hanging various weights from it and measuring the corresponding extensions. The results are shown below.

weight/N 0 1 2 3 4 5

extension/mm 0 21 40 51 82 103

a On Fig. 5.1, plot the points from these results. Do not draw a line through the points yet.

Fig. 5.1

[2]

b The student appears to have made an error in recording one of the results.

Which result is this?

[1]

c Ignoring the incorrect result, draw the best straight line through the remaining points.

[1]

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d State and explain whether this spring is obeying Hooke’s Law.

[2]

e Describe how the graph might be shaped if the student continued to add several more weights to the spring.

[1]

f The student estimates that if he hangs a 45 N load on the spring, the extension will be 920 mm. Explain why this estimate may be unrealistic.

[1]

[Total: 8]

Cambridge IGCSE Physics 0625 Paper 3 Q3 November 2009