Test Yourself - Pendulums

	(a)   The diagram shows a simple pendulum at one point in an oscillation (swing).

       (i)    Draw a cross (´) on the diagram so that the centre of the cross marks the position of the centre of mass of the pendulum bob.                                                                             (1 mark)

       (ii)   Draw a circle on the diagram to show the position of the pendulum bob once the pendulum stops swinging.

              Give a reason for your choice of position.                                     (2 marks)

(b)   A student has written the following hypothesis.

              ‘The frequency of a simple pendulum is inversely proportional to the length of the pendulum.’

       If this hypothesis is correct, what would happen to the frequency of a pendulum each time the length is doubled?                                                                                                   (1 mark)

(c)   The student investigated the hypothesis by timing 10 swings of a pendulum. The student repeated this for several different lengths. The student’s experimental data and calculated data are recorded in the table.

Length of pendulum in metres	Time for 10 swings in seconds	Frequency in _____
0.25	10	1.0
0.50	14	0.7
0.75	17	0.6
1.00	20	0.5
1.25	22

       (i)    What is the unit of frequency?                                                         (1 mark)

       (ii)   Calculate the frequency of the pendulum when the length equals 1.25 m.

              Write down the equation you need to use and show how you work out your answer.      (3 marks)

       (iii)  Do the data in the table support the student’s hypothesis?

              Support your answer with a calculation.                                         (1 mark)