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151 Alevel Essay

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GCE Advanced Level and GCE Advanced Subsidiary Level
Paper 9702/01 Multiple Choice

Question Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Key B B A B C D A D B B B D C C D D C B D B

Question Number 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Key A C B B C B B C D B C A C C C A A C A C

General comments The paper proved to be very satisfactory, with good discrimination and a relatively high overall facility. The mean mark was 27.3 with a standard deviation of 6.8. It was particularly pleasing that every question gave positive discrimination. Where a question was difficult it was only the able candidates who were able to answer it. There was no question where weak candidates were able to score more highly than able candidates. Approximately 40% of the candidates scored 30 or more. This shows that the vast majority were well prepared for the test and knew the fundamental facts of most of the syllabus items. Each section of the AS syllabus was covered by the test and the intention is that, within each section, there should be a progression of difficulty starting with easier questions and proceeding to more difficult ones. It is difficult to extract any evidence of candidates running out of time on the test but it is important for Teachers to brief their candidates never to spend an undue length of time on any particular question. If a candidate gets stuck on a question just leave it until the end and come back to it if there is time. In this case, be particularly careful to leave a blank box on the answer sheet, hence ensuring that each subsequent answer goes into the correct box.

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Comments on specific questions Questions 1, 10, 12, 16, 17, 19, 22, 24, 26, 27, 30, 33, 38 and 39 were straightforward and the marks were correspondingly high. Question 2 is on a topic which is one of the most intellectually difficult parts of the syllabus yet still 40% of candidates managed to get it right. There are two alternative ways of thinking about vector subtraction. They are; what needs to be added to vector Y to get vector X or, and more common, but less easy to use in practice, vector Z = vector X + (- vector Y). Algebraic questions generally prove to be more difficult for candidates than arithmetical ones so perhaps more practice needs to be done on questions like Questions 11, (59% correct), 14 (43% correct) and 21 where there were only 16% correct answers, the lowest figure on the paper. Candidates must be careful to answer the question set. It would help if they realised that all the data which they are given is going to be used somewhere in the question. In Question 32 far too many candidates (32%) ignored the factor of 16 and just worked out the resistance of the bulb when hot, 576 Ω. In general, questions on electricity scored less highly than those on other topics. The unfamiliar nature of Question 40 did not discourage candidates. 67% of them managed to get C as the correct response.

Paper 9702/02 Structured Questions

General comments The overall standard of the candidates’ work varied widely. There were some very good answers, showing clear understanding of the underlying concepts and thorough preparation for the examination. On the other hand, some candidates were unaware of basic ideas and consequently, scored very few marks. It was pleasing to note that the general level of explanation given in calculations and descriptive parts of questions is improving. However, questions where a descriptive answer is required are still a general weakness. Candidates could benefit from further practice at such questions. There appeared to be sufficient time for candidates to complete their answers. Where candidates cannot complete a section of a question, they should be encouraged to write down any relevant physics that they know. A blank answer paper will always score zero. Comments on specific questions Question 1 Only a minority of candidates scored full marks in this question and, although two parts could be answered by calculation and not estimation, many scored fewer than two marks. Since estimates were being asked for, the marking scheme allowed for a range of answers. The vast majority of candidates were either within the range or were several powers of ten away from an acceptable answer. For example, in (d), answers varied from 10-4 Pa to 1015 Pa. Question 2 (a) With few exceptions, candidates realised that the zero error would introduce a systematic error. However, their reasoning was frequently suspect. An answer such as ‘because the error is in the instrument’ is insufficient. Candidates should be encouraged to think about such an error as being constant in magnitude and in one direction only. Candidates were expected to state what aspect makes the readings precise (reproducibility of the reading) and what causes the readings to be inaccurate (zero error). This distinction was frequently unclear. An answer such as ‘the readings are precise because a micrometer is a precise instrument’ was not acceptable.

(b)

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Question 3 (a) Candidates should be encouraged to give brief but precise explanations/definitions. Answers from weaker candidates often made reference to ‘weight acting over a region’. It should be realised that ‘the weight may be considered to act at this point’. In part (i), it was surprising how many answers were not correct. Automatically, candidates seemed to think that the readings on the two meters must be equal, rather than consider the equilibrium of the plank. Similarly, in (ii), most showed the centre of gravity at the geometrical centre. In the calculation in part (iii), candidates were expected to state about which point they were taking moments. There were some very good clear answers. Equally, some responses consisted of a series of numbers, not including all of the relevant moments and with the moments taken about a number of different points.

(b)

Answers: (b)(i) 380 N, (iii) 108 cm. Question 4 (a) This section could be answered either by energy considerations or by use of an equation of motion. Both approaches were equally acceptable and the majority of answers were correct. Candidates should be discouraged from using the value of 10 m s-2 for g, unless they are told to do so or they are carrying out an estimate. Using g = 10 m s-2 and then giving an answer to three significant figures is clearly incorrect. In part (i), most candidates actually calculated 90% of the kinetic energy and then equated this with the change in gravitational potential energy. This involved much work and was unnecessary. They should have realised that the new potential energy would be 90% of the initial potential energy and hence the ball would rises to 0.9 times the initial height. It was not uncommon to find, either here or in (c), that the mass was not expressed in kilograms. In part (ii), those who had completed part (i) were usually able to complete this calculation. Answers here were disappointing. With very few exceptions, candidates did not appreciate the vector nature of momentum and consequently subtracted the final momentum from the initial value. Clearly, the consideration of direction should be emphasised. Answers to this section were very disappointing. In general, it was stated that momentum had not been conserved and consequently the collision is inelastic. Others realised that momentum must be conserved and then said that the change calculated is small! There appears to be little understanding that momentum is conserved only in a complete system. Candidates were expected to make reference to the Earth/plate and that the Earth/plate experiences a change in momentum equal in magnitude but opposite in direction to that of the ball.

(b)

(c)

(d)

Answers: (a) 5.6 m s-1; (b)(i) 1.4 m, (ii) 5.3 m s-1; (c) 0.80 N s. Question 5 (a) (b) (c) There were few correct answers here. Many did not give a response or merely ‘moved the piston’. It was expected that the cylinder would be raised vertically. The majority of candidates stated that the piston would be moved out in order to increase the volume. It was not expected that they should make a reference to the speed of the change. As in (b), most candidates gave a correct response.

Question 6 (a) In part (i), most candidates showed the top plate as being positive. Although most answers in part (ii) were correct, a significant minority either did not express the separation in metres or became confused with the algebra when re-arranging the expression E = V/d. The calculation provided very few problems for average and above average candidates. A common error was to assume that the force is given by the product of potential difference and charge.

(b)

Answers: (a)(ii) 360 V; (b) 5.3 ´ 1015 m s-2.

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Question 7 (a) The standard of the drawings frequently indicated that little care had been taken. It was expected that constant wavelength would be indicated. In some diagrams ...

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