Turn over 23 10 A student investigated the behaviour of a spring under tension. The spring was hung vertically with a mass holder attached as shown. metre rule spring mass holder (a) The student measured the length of the spring as he added masses to the holder. The rule was held as shown to measure the distance between the top and bottom coils of the spring. He determined the extension for each value of total mass on the holder. He did this by subtracting the original length of the spring from each extended length. (i) Explain whether this method would produce accurate values for the extensions of the spring. (4) .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. 24 (ii) Explain how the student could modify his method in order to obtain more accurate values for the extensions of the spring. 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(b) In another experiment, the student displaced the mass vertically each time a mass was added to the spring. He used a stopwatch to determine the period of vertical oscillations of each mass. The student used his data to plot a graph of T 2 against m as shown. 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 1.5 1.0 0.5 0.0 m / kg T 2 / s2 Turn over 25 The student expected the graph to be a straight line through the origin. He thought that there may be systematic error due to reaction time. (i) Give an example of another possible systematic error in this experiment. (1) ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... (ii) Another student suggests that to reduce the uncertainty in the value for the period, a data logger connected to a light gate could be used to measure time. Comment on the student’s suggestion. 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(iii) Determine a value for the stiffness of the spring. 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Stiffness of spring = ....................................................... 26 (c) When determining the period of oscillation for each mass, the student measured the time for 20 oscillations. He repeated this measurement to obtain a mean time for 20 oscillations. Explain how the student’s procedure contributed to the accuracy of the measurement. 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(Total for Question 10 = 19 marks) Turn over 27 BLANK PAGE