Cambridge A Level Physics 9702 — 2005 May/June Paper 5 · Variant 1

This document consists of 10 printed pages and 2 blank pages. SPA (MML 8097 3/04) S81478/2 © UCLES 2005 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level PHYSICS 9702/05 Paper 5 Practical Test May/June 2005 1 hour 30 minutes Candidates answer on the Question Paper. Additional Materials: As specified in the Confidential Instructions. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen in the spaces provided on the Question Paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer both questions. You are expected to record all your observations as soon as these observations are made, and to plan the presentation of the records so that it is not necessary to make a fair copy of them. The working of the answers is to be handed in. Marks are mainly given for a clear record of the observations actually made, for their suitability and accuracy, and for the use made of them. Additional answer paper and graph paper should be submitted only if it becomes necessary to do so. You are reminded of the need for good English and clear presentation in your answers. At the end of the examination, fasten all your work securely together. Centre Number Candidate Number Name If you have been given a label, look at the details. If any details are incorrect or missing, please fill in your correct details in the space given at the top of this page. Stick your personal label here, if provided. For Examiner’s Use 1 2 Total

It is recommended that you spend about 60 minutes on this question. 1 In this question you will investigate how the period of oscillation of a loaded steel blade varies with the length of the blade and use the results of your experiment to determine a value for the Young modulus of steel. (a) Use the G-clamp and the small blocks of wood to clamp the steel blade to the bench as shown in Fig. 1.1. The blade has two small 50 g masses attached to one end. You should not disturb the position of these masses during the course of the experiment. Fig. 1.1 (b) (i) Measure and record the distance d from the centre of the masses to the edge of the blocks as shown in Fig. 1.2. You will need to hold the blade horizontal when you make the measurement of d. blocks of wood blade 50g masses G-clamp 2 9702/05/M/J/05 © UCLES 2005 For Examiner’s Use

Fig. 1.2 d = … m (ii) Displace the end of the blade from its equilibrium position and release it so that the strip performs small oscillations in a vertical plane. Make and record measurements to determine the period T of oscillation of the blade. T = … s d 3 [Turn over 9702/05/M/J/05 © UCLES 2005 For Examiner’s Use

(c) Change the value of d and repeat (b)(i) and (ii) until you have six sets of readings of distance d and period T for values of d in the range 0.130 m < d < 0.250 m. Include in your table of results all six sets of values for lg (T / s) and lg (d / m). (d) (i) Plot a graph of lg (T / s) (y-axis) against lg (d / m) (x-axis). (ii) Draw the line of best fit. (iii) Determine the gradient and the y-intercept of this line. gradient = … y-intercept = … 4 9702/05/M/J/05 © UCLES 2005 For Examiner’s Use

5 [Turn over 9702/05/M/J/05 © UCLES 2005 For Examiner’s Use

(e) Theory suggests that T and d are related by a simple power law of the form T = kdn where n and k are constants. Use your answers from (d)(iii) to find the values of n and k. You need not be concerned with the units of these quantities. n = … k = … A theoretical treatment of this oscillator suggests that where M is the mass attached to the end of the blade, E is the Young modulus, b is the width of the blade and t is the thickness of the blade as shown in Fig. 1.3. Fig. 1.3 t b 16
2M k = √––––– Ebt 3 6 9702/05/M/J/05 © UCLES 2005 For Examiner’s Use

(f) (i) Measure the values of b and t. The measurement of t should be made on a part of the blade where there is no tape. b = … m t = … m (ii) State the name of the instrument used to measure t. … (iii) Estimate the percentage uncertainty in the value of t 3. percentage uncertainty in t 3 = … % (g) Determine a value for E. Include an appropriate unit. E = … 7 [Turn over 9702/05/M/J/05 © UCLES 2005 For Examiner’s Use

It is recommended that you spend about 30 minutes on this question. 2 Many homes have smoke detectors fitted to the ceilings of certain rooms to provide an early warning of a fire. These detectors contain a weak radioactive source that ionises the air between two metal plates. See Fig. 2.1. Fig. 2.1 A low voltage battery in the detector causes the ions to move. This produces a very small ionisation current in a circuit containing the battery and the plates. Any reduction in this ionisation current due to smoke is detected and an alarm sounds. An airline company wishes to install some of these smoke detectors in its aircraft and needs to know if changes in air pressure will affect the ionisation current. Design a laboratory experiment to investigate how the ionisation current depends on air pressure. You should draw a detailed labelled diagram showing the arrangement of your apparatus. In your account you should pay particular attention to (a) the type of source used in the investigation (i.e. whether it is an alpha, beta or gamma emitter) giving a reason for your choice, (b) how the ionisation current would be measured (given that it is very small), (c) the method of changing and measuring the air pressure, (d) the procedure to be followed, (e) any safety precautions that you would take. 8 9702/05/M/J/05 © UCLES 2005 For Examiner’s Use

Diagram … … … … … … … … … 9 [Turn over 9702/05/M/J/05 © UCLES 2005 For Examiner’s Use

… … … … … … … … … … … … … … … … … … … … … … … … … … … … 10 9702/05/M/J/05 © UCLES 2005 For Examiner’s Use

BLANK PAGE 12 9702/05/M/J/05 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Level MARK SCHEME for the June 2005 question paper 9702 PHYSICS 9702/05 Paper 5 (Practical Test), maximum raw mark 30 This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. This shows the basis on which Examiners were initially instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the Examination. • CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the June 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Grade thresholds for Syllabus 9702 (Physics) in the June 2005 examination. minimum mark required for grade: maximum mark available A B E Component 5 30 24 22 14 The thresholds (minimum marks) for Grades C and D are normally set by dividing the mark range between the B and the E thresholds into three. For example, if the difference between the B and the E threshold is 24 marks, the C threshold is set 8 marks below the B threshold and the D threshold is set another 8 marks down. If dividing the interval by three results in a fraction of a mark, then the threshold is normally rounded down.

June 2005 GCE A LEVEL MARK SCHEME MAXIMUM MARK: 30 SYLLABUS/COMPONENT: 9702/05 PHYSICS Paper 5 (Practical Test)

Page 1 Mark Scheme Syllabus Paper A LEVEL – JUNE 2005 9702 5 © University of Cambridge International Examinations 2005 1 (b) (ii) Repeats of raw time [1] (c) Readings [3] Write the number of readings as a ringed total by the results table. 6 sets of readings scores 1 mark. Do not award this mark if wrong trend or no trend. Check a value for lg(T/s) and a value for lg(d/m). Underline checked values. Ignore small rounding errors. Allow d in cm. Tick if correct; 1 mark each. If incorrect then write in correct value. Ln loses one mark only. If no value for N then the mark for lg(T/s) cannot be scored. If minor help is given, then -1. If excessive help is given then -2. Please indicate when help has been given to a candidate by writing SR at the top of the front page of the candidate's script. Also, please indicate the type of help that has been given by writing a brief comment by the table of results. At least two readings > 10 s [1] Column headings [1] There must be some distinguishing mark between the quantity and its unit. Please
each correct column heading to show that it has been seen. Ignore the column headings for lg(T/s) and lg(d/m) Consistency of raw readings in the table of results [1] Apply to d and raw times only. Expect to see raw times to either 0.01 s or 0.1 s. Expect to see all the values of d given to the nearest millimetre. Indicate using
C at the foot of each column of raw readings if correct. (d) (i) Axes [1] Each axis must be labelled with a quantity. Scales must be such that the plotted points occupy at least half the graph grid in both the x and y directions. Do not allow more than 3 large squares between scale markings. Do not allow awkward scales (e.g. 3:10, 6:10, 7:10, etc.). Do not award this mark if the axes are inverted (i.e. lg(d/cm) vs lg(T/s)), but ecf. Plotting of points [1] Count the number of plots on the grid and write this value by the line and ring it. Do not allow plots in the margin area. The number of plots must correspond to the number of observations. Do not award this mark if the number of plots is less than the number of observations. Check one suspect plot. Circle this plot. Tick if correct. If incorrect then mark the correct position with a small cross and use an arrow to indicate where the plot should have been. Allow errors up to and including half a small square.

Page 2 Mark Scheme Syllabus Paper A LEVEL – JUNE 2005 9702 5 © University of Cambridge International Examinations 2005 (ii) Line of best fit [1] There must be a reasonable balance of points about the line of best fit. If one of the plots is a long way from the trend of the other plots then allow this plot to be ignored when the line is drawn. (iii) Measurement of gradient [1] The hypotenuse of the triangle must be greater than half the length of the drawn line. Read-offs must be accurate to half a small square and ratio must be correct. Please indicate the vertices of the triangle used by labelling with ∆. y-intercept [1] Check the read-off. Accept correct substitution from a point on the line into y = mx + c. (e) lg T = n lg d + lg k [1] This can be implied from the working. Value for n (from gradient) [1] Value for k (only from 10y-intercept) [1] (f) (i) Value of t ( ± 0.05 mm of SV) or ± 0.05 mm of extremes if range given [1] If POTE do not award this mark. (ii) Micrometer screw gauge/micrometer/screw gauge [1] (iii) Percentage uncertainty in t3 [1] ∆t
ratio, x100 and ‘x 3’ must be correct. ∆t can be 0.005 mm, 0.01 mm, 0.02 mm or half the range. (g) Value of E [1] Check the substitution, working and consistency of units. Must be in range from 5.0 x 1010 to 5.0 x 1011 Pa. Allow M = 0.05 kg or 0.10 kg. Bald answer for E scores zero. Unit of E (Pa or N m-2) [1] [Total: 20 marks]

Page 3 Mark Scheme Syllabus Paper A LEVEL – JUNE 2005 9702 5 © University of Cambridge International Examinations 2005 2 A1 Use of alpha emitter as source (one mark), with a reason [2] (strongly ionising) (one mark). These are independent marks. Do not award these marks if the source is not sensible (e.g. smoke producing alpha particles) A2 Correct circuit showing milliammeter/microammeter/galvanometer [1] Do not allow ammeter. Accept ‘sensitive ammeter’. A power supply must be shown. A3 Use of Bourdon gauge/pressure gauge/manometer/barometer [1] Accept pressure sensor + datalogger. Do not allow vague ‘pressure metre’. Could be shown on the diagram. B1 Change air pressure using pump (could be shown on diagram) [1] B2 Diagram showing ‘closed box’ surrounding the equipment. [1] do not award this mark if the gauge is not measuring the pressure in the box. B3 Procedure [1] Measure ionisation current and P; change air pressure (and measure new pressure and ionisation current). This mark can be scored even if the design is unworkable. Accept a table. C1/C2 Two safety precautions [2] e.g. use source handling tool store source in lead lined box when not in use do not point source at people/do not look directly at source use safety goggles when dealing with low/high pressures Do not allow vague ‘safety goggles’ without clarification container must be strong enough to withstand high/low pressure use safety screens in case of implosion/explosion Do not allow lead suits/lead lined rooms/lead gloves/lead lined expt. etc. One mark for safety relating to radiation. One mark for safety relating to pressure. D Any good/further detail [1] Examples of creditworthy points might be: Use high voltage as current is small Use GM tube and scalar/ratemeter to monitor activity to ensure that it does not change Use of source of long half-life Place source close to plates (as range of alpha in air is small) Tap gauge when taking readings (in case needle sticks) Fix position of source relative to plates Separation of plates constant Allow other valid points. [Total: 10 marks]