CAIE Physics (9702)

A spring is attached to a strong cylindrical magnet of length L and cross-sectional area A. The magnet is placed on thin card on top of a magnetic sheet on the bench, as shown in Fig. 1.1. spring magnetic sheet bench cylindrical magnet card The thickness of the card is t. The magnetic flux density at one of the poles of the magnet is B. A force is applied upwards to the spring. The extension of the spring when the magnet just leaves the card is s. It is suggested that s is related to t by the relationship ks = ALBZ where k is the spring constant of the spring and Z is a constant. Plan a laboratory experiment to test the relationship between s and t. Draw a diagram showing the arrangement of your equipment. Explain how the results could be used to determine a value for Z. In your plan you should include: Diagram

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A student investigates the resonant frequency of a m etal rod. The metal rod of length L is suspended from two rubber loops. A sensitive microphone with a cone is positioned at one end of the rod. The microphone is attached to an oscilloscope, as shown in Fig. 2.1. bench rodhammer rubber loop to oscilloscope cone microphone stand Fig. 2.1 (not to scale) The rod is hit gently with a hammer. The period T of the trace produced on the oscilloscope is determined. The experiment is repeated for different values of L. It is suggested that T and L are related by the equationT = where C and n are constants.

A graph is plotted of lg T on the y-axis against lg L on the x-axis. Determine expressions for the gradient and y-intercept. gradient = y-intercept = [1] * 0019655344405 *

Values of L and T are given in Table 2.1. Table 2.1 L / cm T / 10 s lg (L / cm) lg (T / 10 54 24 ± 1 70 32 ± 1 86 39 ± 1 108 49 ± 2 140 64 ± 2 167 74 ± 2 Calculate and record values of lg (L / cm) and lg (T / 10 s) in Table 2.1. Include the absolute uncertainties in lg T.

(i) Plot a graph of lg (T / 10 s) against lg (L / cm). Include error bars for lg T.

Draw the straight line of best fit and a worst acceptable straight line on your graph. Label both lines.

Determine the gradient of the line of best fit. Include the absolute uncertainty in your answer. gradient = [2] * 0019655344406 * 1.7 1.35 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.8 1.9 2.0 lg (L / cm) lg (T / 10 2.1 2.2 2.3 * 0019655344407 *

Determine the y-intercept of the line of best fit. Include the absolute uncertainty in your answer. y-intercept =

Using your answers to

, determine the values of n and C. Include the absolute uncertainties in your values. You need not be concerned with units. n = C =

The experiment is repeated. Determine the length L of the rod that gives a value of T of 0.10 ms. L = cm [1] [Total: 15] To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. * 0019655344408 *, ,