Cambridge A Level Physics 9702 — 2002 Oct/Nov Paper 3 · Variant 1

This question paper consists of 5 printed pages and 3 blank pages. SP (SM/CG) S21699/1 © CIE 2002 [Turn over CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level PHYSICS 9702/3 PAPER 3 AS Practical OCTOBER/NOVEMBER SESSION 2002 1 hour 15 minutes Candidates answer on the question paper. Additional materials: As specified in Instructions to Supervisors Graph paper TIME 1 hour 15 minutes INSTRUCTIONS TO CANDIDATES Write your name, Centre number and candidate number in the spaces at the top of this page and on any separate answer paper used. Answer the one question. Write your answers in the spaces provided on the question paper. 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. INFORMATION FOR CANDIDATES 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. Candidate Centre Number Number Candidate Name FOR EXAMINER’S USE

2 9702/3/O/N/02 1 In this question you will investigate how the period of torsional oscillations of a bar magnet suspended above a fixed bar magnet changes with the separation between the two magnets. (a) (i) Fix one of the magnets to the bench top using tape or Blu-tack. (ii) Suspend a second magnet using a cradle and thread so that it lies in a horizontal plane about 50 cm below the point of suspension. The distance d between the bottom of the suspended magnet and the top of the fixed magnet should initially be about 5 cm. The base of the stand should be as far as possible from the fixed bar magnet. The arrangement is shown in Fig. 1.1. Fig. 1.1 (b) (i) Measure and record the distance d. (ii) Gently rotate the suspended magnet and release it so that it performs small torsional oscillations in a horizontal plane, as shown in Fig. 1.2. Fig. 1.2 Make and record measurements to determine the period T of these oscillations. (iii) Change the value of d and repeat (i) and (ii) until you have six sets of readings for T and d where 10 cm ≥d ≥3 cm. top view small blocks of wood point of suspension cotton suspended bar magnet fixed bar magnet d about 50cm

3 9702/3/O/N/02 [Turn over (c) It is suggested that T and d are related by an expression of the form T = kd + c where k and c are constants. (i) Plot a graph of T (y-axis) against d (x-axis). (ii) Determine the gradient and y-intercept of the line of best fit. (iii) Use your answers from (ii) to find values for k and c. Include appropriate units in each case. (d) A student suggests that T is directly proportional to d. Explain whether or not the results of your experiment would support this suggestion. … … … … (e) (i) Use the results of your experiment to calculate the period of oscillation of the suspended magnet for a separation d = 5 mm. period of oscillation = … (ii) Give two reasons why, in practice, it would not be possible to measure this time directly. 1 … … 2 … … For Examiner’s Use

4 9702/3/O/N/02 Measurements and calculations For Examiner’s Use M R A

5 9702/3/O/N/02 Graph grid For Examiner’s Use G

CAMBRIDGE INTERNATIONAL EXAMINATIONS NOVEMBER 2002 GCE Advanced Subsidiary Level UNIVERSITY of CAMBRIDGE Local Examinations Syndicate

Page 1 of 3 Mark Scheme AS Level Examinations - November 2002 Syllabus Paper 9702 3 M1 M2 M3 M4 R1 R3 G1 G2 G3 Measurements Measurements Write the number of readings as a ringed total by the results table. One mark for each set of readings to a maximum of 6 marks Check a value for T. If incorrect then -1. Repeated readings For each value of T there must be at least two values of t. An average value must be calculated. At least half the raw times > 10s Quality of results Judge by scatter of points about the line of best fit. Results Column headings Each column heading must contain a quantity and a unit. Consistency Apply to tand d. Values of d must be given to the nearest millimetre. Values of t must be given to the same number of decimal places. Do not allow t to be given to a whole number of seconds or 0.001 s. Sf ink Accept two or three significant figures only. Graphical work Axes Scales must be such that the plotted points occupy at least half the graph grid in both the x and y directions. Sensible scales must be used (i.e. 2:10 or 5:10 etc.) Plotting of points Write the number of plots as a ringed number on the graph grid. All observations must be plotted. The plots must be accurate to half a small square. Line of best fit Judge by scatter of points about the line of best fit. Do not allow a straight line to be drawn through a curved trend.

Page 2 of 3 Mark Scheme Syllabus | Paper AS Level Examinations — November 2002 9702 3 G4 G5 Al A2 A3 A4 AS AG S1 $2 Determination of gradient The hypotenuse of the triangle must be greater than half the length of the line which has been drawn. Check the read-offs. Intercept The value may be read or calculated from y = mx + c. Analysis k = candidate's gradient c = candidate's y-intercept Unit of k and unit of c correct Sensible suggestions relating to direct proportionality One mark for ‘straight line’ ideas. Correct working to give period when d= 5 mm Oscillations are too quick to time manually Magnets may stick together at this small separation One mark each. 25 marks in total Special cases Graph gives a clear curved trend of plots; M4 = 0; G3 = 0 (if straight line drawn); A4 can only score 1/2 max. Negative value of T when d= 5 mm; A5 = 0. Allow ecf into A6 if possible.

Page 3 of 3 Mark Scheme Syllabus | Paper | AS Level Examinations —- November 2002 9702 3 | Sample results. Gradient = 0.143 y-intercept = -0.04 Hence k = 0.143 s cm and c = -0.04.s