€¦ · web viewthis candidate received full marks (2) ... even though the word 'transfer' is...

Q1.

(c) (i)

There were three explicit calculations on this paper - 2ci, 3aiii and 5aii. All were good discriminators near the C/D boundary. Near the A boundary nearly all scored full marks.

Results Plus: Examiner Comments

This candidate received full marks (2) for the numerical calculation plus 1 mark for the unit. Total score: 3 marks.


Without the unit, this answer is worth 2 marks.


Although some 'working' is shown, the absence of a written equation cannot help to score any marks for substitution - score 0.

Results Plus: Examiner Tip

Copy the equation you intend to use from the data sheet provided. In this case however, the incorrect use of 600 instead of 10 for g would have prevented you scoring.


When asked for, the unit mark can be scored independently of the numerical working. This response was therefore worth 1 mark.


Think what you are calculating and recall the unit for that quantity - ie distance - m, force - N, power - W etc.

(c) (ii)

This item followed a multiple choice item (2a) in which two of the options covered large periods of time (before ...) and the key and one other showed instants of time (when ...). The multiple choice item produced good discrimation by reflecting performance on the paper as a whole.


This response expressed the point needed concisely and scored the mark.

Other correct responses included 'after falling 50 m' and 'just as the cord becomes straight'.

The stem describes how the cord 'becomes straight and starts to stretch when he has fallen 50 m.'

One common misconception involved mixing up KE and GPE.


This is an exact single moment in time but was incorrect and scored 0.

Other responses were vague such as 'while falling', 'when stretching' or 'at the bottom' (of what).

(c) (iii)

The inefficiency of energy transfers was tested here.

Many candidates presented either the energy transfer or the reason for this. Few presented both.


The idea that the surroundings are heated scored 1 mark and 'due to air resistance' scored the second.

Marks are often lost through the use of the general words 'it', 'they' etc.


The 'it' here could refer to some energy, heat energy etc.


When writing, try to avoid using words such as 'it' and 'they'. Take the little extra time needed to say exactly what you mean.

A variety of incorrect numerical responses were given for this. The most common referred to the fact that calculations of KE involve the factor of 1/2 and 'so must be less than the other'. Another example involved the gravitational field strength.


This scored 0.

Q2.

(ii)

The third explicit calculation involved the transposition of an equation of general form X = Y/Z.


There was no hesitation in awarding this the full (3) marks.

Again, the transposition and substitution marks can be awarded in either order.


Here, the substitution is carried out correctly before the incorrect transposition and so scores 1 mark.


The lowest part of this response could be said to show the correct transposition, substitution and evaluation. However, this was, in effect, a list of possible things to do with the two numbers - essentially giving the examiner a choice. The candidate then wrote the incorrect choice in the answer space. This scored 0 marks.

Q3.No Examiner's Report available for this question

Q4.No Examiner's Report available for this question

Q5.

This six-mark question presented candidates with the opportunity to show their power of written communication in a familiar situation. There were quite a few examples of candidates presenting pre-prepared but irrelevant answers about breaking (sic) distances etc and the use of air bags and crumple zones.

The vast majority were able to compare the relative decelerations of the driver, car and shopping, although this was little more than common observation from an every day situation. Since this was a science examination, various degrees of explanation were needed to progress to higher levels. As the question was open-ended, there was opportunity to explain what happened in terms of forces and/or energy and/or momentum.


For this, there is limited comparison of the decelerations of the person and the shopping. There is little more here than common observation. It is a level 1 answer for 2 marks. To move to level 2, some science needs to be used to explain at least one of the decelerations.


There is a clear comparison of the decelerations of all three objects. Combined with the effect of the seat belt on the rate of change of momentum, and the explanation of the effect of rapid change in momentum on the shopping, shows sufficient science to move this into a level 2 answer worth 4 marks. A little more science, for example in terms of stretching of the seat belt or further explanation of the shopping continuing at the same velocity, would have raised this to a level 3 response.


There is insufficient relevant science or everyday observation of the effect to score any marks. Technical terms such as kinetic energy, momentum and conserved are used but convey little scientific understanding. This scores 0 marks.


There is good comparison of the relative decelerations of all three objects and some science implied during discussion of the idea of inertia or conservation of momentum for the shopping bag. Misspellings of brakes and immediately are not serious enough to reduce the mark for quality of written communication. This is a level 2 answer scoring 4 marks despite the erroneous statement about the driver being forced forward.

Q6.

(a)

In this energy transfer question examiners were looking for three ideas:

a transfer between GPE and kinetic as Andrew descends

a transfer between KE and thermal during the decent

what happens to the energy when he has stopped.

Most candidates failed to score. About a third of candidates scored 1 mark or better with only a very few scoring full marks.


Even though the word 'transfer' is not used, this answer was sufficient to score all 3 marks.

(b)(i)(ii)

These were straightforward questions involving the use of equations. The vast majority of candidates scored full marks.

(b)(iii)

This question tested the idea that force is proportional to rate of change of momentum. It proved to be a good discriminator. The idea did not have to be formally stated. The following examples show some ways in which full marks could be scored.


This is a perfectly acceptable way of relating force to the time it takes to reduce the momentum. It scored full marks.


This is closer to the formal statement of Newton's second law. It also scored full marks.


This is a very good, well expressed response, which scored full marks.


In a situation like this, write down the relevant equation:

force = change in momentum time

then use it to construct your written answer.

Q7.

(a) (iii)

In this type of "show that" question, candidates can score full marks in two ways.

They can use the values supplied ( in this case 71J and 27 kg) and subsitute those into the equation given inside the fornt cover. They can then transpose this expression and perform any other required steps ( in this case finding a square root) to arrive at a result which can be compared with the "answer" ( in this case 2.3 m/s)

An alternative and mathematically simpler method is to use the "answer" of 2.3 m/s and the given value of mass (27 kg) in the expression for kinetic energy. They can then evaluate this expression and compare the result with the KE given in the question. This requires no transposition and no calculation of a square root.

This candidate has chosen to calculate the velocity from the KE and the mass.


Although v2 is missing in the second line and 71 does not equal 0.5 x 27, the candidate's intentions are clear and the value of 2.293 could only have been obtained by the correct mathematics. Full marks


Make sure that values on each side of an equals sign really are equal to each other.

Here, the candidate has chosen the easier route.


A simple response which scores full marks.

(b)

This was the least well-answered question on the paper. It seemed that many candidates did not read the introduction carefully and gave answers which either implied or stated that the swings were decreasing in amplitude because the brother was still pushing but getting tired. Many other candidates tried to give explanations using the concepts of momentum, forces and acceleration rather than describing changes in kinetic energy. Another common misconception was that the kinetic energy was smallest when the swing was at the bottom.

Examiners were looking for an explanation which described a continuous transfer between kinetic energy and gravitational potential energy. They were also looking for an understanding that this transfer was not perfect and that energy was being dissipated to the surroundings resulting in a gradual loss of kinetic energy.

Rather than scoring individual marking points, examiners arrive at a judgement of the overall level of the response; taking into account how scientific terms are used to give a complete explanation.

This is best shown by the examples below.

A level 1 response would be a limited explanation which correctly stated some facts.


This is a simple explanation which correctly states how kinetic energy changed over the cycle and where the kinetic energy was greatest. The use of language is suitable for this level. 2 marks

A Level 2 response would be a simple explanation which linked facts together to explain one feature of the graph; either why the kinetic energy decreased and increased over one swing or why the maximum kinetic energy decreased over several swings.


This answer gives a clear description of the transfer between kinetic and gravitational potential energy. Although the candidate has mentioned the decrease in maximum kinetic energy, this has not been explained. Spelling, punctuation and grammar is suitable for this level. 4 marks.


This response explains why the maximum kinetic energy decreases over several cycles and is at level 2. It does not mention the transfer between kinetic energy and gravitational potential energy. It scored 4 marks.

Level 3 responses gave a full explanation of both features of the graph.


A well written response which explains both the transfer between kinetic energy and gravitational potential energy and the gradual decrease in maximum kinetic energy. All scientific terms are used correctly. Full marks at level 3.

Candidates need to be especially careful with their English as well as their Physics.


Although the scientific explanation is correct and is at level 3, the answer has many errors of spelling, punctuation and grammar. 5 out of 6 marks only.


Make sure that you use capital letters and punctuation correctly. If you do not then you will lose marks in this type of question.

€¦ · web viewthis candidate received full marks (2) ... even though the word 'transfer' is...

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