Moments (Cambridge (CIE) IGCSE Physics)

Exam Questions

3 hours36 questions
1a2 marks

A student investigates the balancing of a metre rule.

Fig. 1.1 shows the arrangement.

p6-moments

The student places the metre rule on the pivot at the 50.0 cm mark. He places an object Q on the metre rule with its centre at the 90.0 cm mark. He places a load of weight P = 2.0 N on the metre rule and adjusts the position of the load so that the metre rule is as near as possible to being balanced.

He measures the distance x from the centre of the load to the pivot.

He repeats the procedure using loads of weight P = 3.0 N, 4.0 N, 5.0 N and 6.0 N. All the values of P and x are recorded in Table 1.1.

P/N

x/cm

1 over x divided by fraction numerator 1 over denominator c m end fraction

2.0

40.0

3.0

27.0

4.0

20.0

5.0

15.9

6.0

13.3

Calculate, and record in Table 1.1, the values of begin mathsize 14px style 1 over x end style

1b4 marks

Plot a graph of P / N (y-axis) against 1 over x space divided by 1 over cm (x-axis). Start both axes at the origin (0,0).      

pCZsL3G__p6-graph
1c2 marks

In this experiment, xmax , the maximum possible value for x is 50.0cm. Calculate 1 over x subscript m a x end subscript.                             

1 over x subscript m a x end subscript = .................................................. size 14px 1 over size 14px cm

Use the graph to determine the minimum value of P required to balance the metre rule in this experiment. Show clearly on the graph how you determined this value.

           

minimum value of P = ..................................................... 

1d1 mark

In this experiment, the width of object Q is slightly greater than the width of the metre rule. Explain briefly how you would place the object Q as accurately as possible on the 90.0 cm mark of the metre rule. You may draw a diagram.

1e2 marks

Extended tier only

In this experiment, it is difficult to determine the exact position of the load that will make the metre rule balance.

                         

(i) Explain briefly why this is difficult.

[1]

                    

(ii) Explain briefly how you would find the best position of the load that will make the metre rule balance.

[1]

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2a4 marks

Extended tier only

A student is determining the weight of a metre rule using a balancing method.

  Fig. 1.1 shows the apparatus.

p2-1a

The student places the metre rule on the pivot. He places the load P on the metre rule at the 90.0 cm mark. Keeping load P at the 90.0 cm mark, he adjusts the position of the metre rule on the pivot so that the metre rule is as near as possible to being balanced.

  He records the distance a from the 90.0 cm mark to the pivot.

  He records the distance b from the pivot to the 50.0 cm mark.

  He repeats the steps, placing the load P at the 85.0 cm, the 80.0 cm, the 75.0 cm and the 70.0 cm marks.

  The readings are shown in Table 1.1.

Table 1.1

a/cm

b/cm

21.0

19.1

18.0

17.2

16.0

14.1

13.0

11.8

10.5

9.5

Plot a graph of a/cm (y-axis) against b/cm (x-axis). You do not need to begin your axes at the origin (0,0).

p2-1b
2b2 marks

Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information.

  

G = ........................................................

2c2 marks

Calculate the weight W1 of the metre rule using the equation W1 = G × P, where P = 1.0 N.

 

W1 = ........................................................ 

2d1 mark

Extended tier only

Suggest one practical reason why it is difficult to obtain accurate readings for a and b in this type of experiment.

2e1 mark

The student measures the mass of the rule on a balance. Write down the mass m shown on the balance in Fig. 1.2 to the nearest gram.

p2-1c

 m = ..................................................... g

2f1 mark

(i) Calculate the weight W2 of the metre rule using the equation W2 = mg, where g = 9.8 N/ kg.

  

W2 = .................................................... N [1]

 

(ii) State and explain whether this value of W2 can be considered equal to the value of W1 obtained in part (c) within the limits of experimental accuracy.

[1]

 

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3a1 mark

Extended tier only

A student is determining the mass of a metre rule by a balancing method.

atp-1

 

He is using the apparatus shown in Fig. 1.1.

He places the metre rule on the pivot and then places block Q with its centre at the 95.0 cm mark. The student stated that it is difficult to place the mass accurately at the 95.0 cm mark.

 Explain how the student could overcome this. You may draw a diagram to help your explanation.

3b2 marks

The student keeps block Q at the 95.0 cm mark and adjusts the position of the metre rule on the pivot until the metre rule is as near to being balanced as possible.

Describe a method to find the point at which the metre rule is as near to being balanced as possible.

3c7 marks

The student determines the distance a between the centre of block Q and the 50.0 cm mark and also the distance b between the centre of block Q and the pivot.

He repeats the procedure for positions of block Q at the 90.0 cm, 85.0 cm, 80.0 cm and 75.0 cm marks. His results are shown in Table 1.1.

Table 1.1

position of Q/cm

a/cm

 b/cm

95.0

45.0

39.0

90.0

40.0

34.3

85.0

35.0

30.0

80.0

30.0

25.2

75.0

25.0

21.4

(i) Plot a graph of a/cm (y-axis) against b/cm (x-axis). You do not need to start your axes at the origin (0,0).

atp-2

[4]

(ii) Determine the gradient G of your line. Show clearly on the graph how you obtained the necessary information.

 

G = ...........................................................[1]

(iii) Calculate the mass MR of the metre rule using the equation

M subscript R equals fraction numerator M over denominator open parentheses G space minus space 1 close parentheses end fraction,

where M = 20 g. Record the value for MR to a suitable number of significant figures for this experiment.

 

MR = ...........................................................[2]

3d1 mark

Two students carry out the experiment correctly but with different values for the mass of block Q. One student obtains values of b that are larger than those obtained by the other student.

State and explain whether the larger values of b are likely to produce a more accurate value for the mass of the metre rule.

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4a4 marks

A student is determining the mass of a load using a balancing method.

  Fig. 1.1 shows the apparatus.

p4-1a

The load X has been taped to the metre rule so that its centre is exactly over the 90.0 cm mark. It is not moved during the experiment.

  A mass m of 40 g is placed on the rule and its position adjusted so that the rule is as near as possible to being balanced with the 50.0 cm mark exactly over the pivot. Fig. 1.2(a) shows part of the rule when it is balanced.

  The procedure is repeated for a range of masses. Fig. 1.2(b) – (e) shows the rule when balanced for values of m of 50 g, 60 g, 70 g and 80 g.

 

p4-1aii

(i) Use Fig. 1.2 to determine d, the distance between the mass and the pivot at balance, for each value of m. Record your results in Table 1.1.

[3]

m/g

d/cm

1 over d divided by 1 over cm

40

 

 

50

 

 

60

 

 

70

 

 

80

 

 

 

(ii) For each value of d, calculate 1 over d and record it in the table.

[1]

4b2 marks

Describe one difficulty the student might have when carrying out this experiment, and how he might overcome this difficulty.

4c4 marks

Plot a graph of m/g (y-axis) against 1 over d divided by 1 over cm (x-axis).

 

p4-1c
4d1 mark

Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information.

 

G = .......................................................... 

4e1 mark

Determine the mass μ, in grams, of the load X. Use the equation mu space equals fraction numerator space G over denominator 40.0 end fraction

 

μ = ....................................................... g 

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