WJEC Physics for AS Level Student Book 2nd Edition

6 WJEC Physics for AS Level Mark allocations for question parts The mark allocation for each question part is given in square brackets, e.g. State the principle of conservation of momentum. [2] The mark allocation gives a good clue to the detail required in your answer. The [2] is a good clue that there are two aspects to the answer. In this case your answer should include: 1. a statement that the (vector) sum of the momenta remains the same, and 2. the conditions, i.e. in a closed system or if no resultant external force acts. On some occasions, a question may only have one mark, but still require both points to be made . Question structure Most questions are structured, having several parts with a linking theme. The way these parts are arranged gives a clue to their relationship to one another. For example, look at question 1 of the Unit 1 Exam practice questions. It has the following structure: 1. (a) (b) (i) (ii) (c) Part (a) asks you to write down an equation. This shows you the physics ideas you will need to employ in answering the question – in this case, moments. Part (b) is in the same question, so the hint in part (a) applies. The two subsections (i) and (ii) are closely related, a fact emphasised in this case by the word ‘hence’ in part (ii). Part (c) is less directly related than (b)(i) and (ii) but it is still about moments. Sometimes there is an extra level of subdivision. For example, look at question 1 of the Unit 2 Exam practice questions: Part 1(a)(iii) has two parts, labelled (I) and (II). All this structure is to guide you through what might otherwise be a lengthy multistage calculation. Without it, you are in danger of starting off in an unhelpful direction, getting lost in the undergrowth, and ending up with an incorrect answer. Answering QER questions QER (Quality of Extended Response) questions test how logically you can present a detailed piece of physics. There will be at least 12 answer lines and perhaps a space for a diagram. Many QER questions ask for a standard piece of knowledge, i.e. it is AO1 and you should know it. For example, question 5 in the Unit 1 Exam practice questions asks for the information which can be gained from the spectrum of a star. Your job is to take what you know and write it down in a logical, structured way. You should pay attention to both your spelling and grammar as well as the accuracy of physics in your response. A common QER question is to ask for the method for one of the assessed practicals, e.g. Describe an experiment to measure the acceleration of a freely falling object. [6 QER] Sometimes QER questions ask about practical work other than the specified practicals. These involve designing the method yourself and so are AO3, e.g. Explain what properties of light from a laser can be determined using polarisation and interference. Give practical details. [6 QER] Synoptic questions In Units 3 and 4 of the A level specification, you will encounter questions which use ideas from AS Units 1 and 2. These are called synoptic questions. This means that the material contained in this book will still be useful in your year 13 studies. Calculation questions Physics exams always have lots of calculations. In fact a minimum of 40% of the marks for Units 1 and 2 are for maths. In calculations you often have to do several things: selecting equations, substituting values, doing some algebra, calculating, giving an answer with a correct unit. It is always good practice to give the working when calculating the answer to a question. Look at this example: A cube, with sides of length 0.30 m has a mass of 120 kg. Calculate its density. [2] The following students have the same wrong answer: Student 1: Density = Mass Volume = 120 kg (0.30 m) 3 ✓ = 1330 kg m í3 ✗ Student 2: Density = 1330 kg/m 3 ✗✗ Student 1 gets a mark because she inserted the values correctly into the equation. She squared the 0.30 m instead of cubing it and so loses the second mark. Student 2 has probably done the same things but without the evidence cannot be awarded the first mark. Practical skills questions Each unit exam has a minimum of 15% of the marks for practical skills. These are for recalling the methods used in the specified practicals (AO1) and the way the results are analysed, for analysing data, drawing conclusions and suggesting improvements (AO2 and AO3).