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In this experiment, I will investigate what affects the frequency of a pendulum. Pendulum clocks have been used to keep time since 1656 and were the first clocks made to have any sort of accuracy.

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Introduction

Physics Coursework- Investigation on Pendulums

Introduction

In this experiment, I will investigate what affects the frequency of a pendulum.  Pendulum clocks have been used to keep time since 1656 and were the first clocks made to have any sort of accuracy.  Clock designers had to face and solved a number of interesting problems to create accurate timekeeping devices.  Today I will investigate what variables could affect the period of the pendulum.  I will change the independent variable 5 times, so as to get sufficient results.

Independent Variable

Predicted effect on Frequency

1. Increase in mass of pendulum

Decrease frequency

2. Increase the length of the swing

Decrease frequency

3. Change aerodynamics (smooth)

Increase frequency

4. Increase width of displacement.

Increase frequency

5. Increase height of clamp stand.

No effect

image00.png

Reasons for my predictions

  1. Increase in mass of pendulum:

When the mass of the pendulum is increased, I think the frequency is likely to decrease.  This is because if the pendulum is heavier, it is inclined to move slower.

  1. Increase the length of the swing:

If the swing is longer, the arc of the circle, which the pendulum traces, will be longer, so the swing will take longer.

  1. Increase the width of displacement:

...read more.

Middle

20

19

19.7

50

19

21

20

20

60

20

21

20

20.3

70

21

19

20

19.7

80

20

20

19

19.7

90

20

20

21

20.3

100

19

22

20

20.3

Overall average oscillations = 20.03 oscillations

My prediction was wrong, the weight of the Bob does not have an effect on the number of periods the bob does. (see the graph)

2.Increase width of displacement:

In the next test, I find out whether the angle of displacement really does increase the frequency of the pendulum.

  1. I used the same equipment as in the last experiment, and it was set up in the same way.  I used string, with a length of 15cm (as before) and a stand at 20cm from the surface of the table (as before).  The bob I used was 50g in weight.
  1. I raised the bob to exactly 90 degrees, measuring with a protractor.  
  1. As before, I let it go, not pushing it, at the same time as starting the stop clock.
  1. I counted how many oscillations the pendulum made.  I repeated this three times.
...read more.

Conclusion

Results

Number Of Oscillations in 20 Seconds

Length of string (cm)

1st

Attempt

2nd

Attempt

3rd

Attempt

Average

5

34

36

32

34

10

27

28

26

27

15

25

23

22

23.3

20

22

20

21

21

25

21

18

20

19.6

30

18

16

17

17

35

16

14

14

14.7

40

9

8

10

9

45

7

6

7

6.7

50

5

4

4

4.3

From this table, I can clearly see a different pattern than those of the other two tables.  This clearly shows that the length of the string used, does affect the number of oscillations the pendulum makes.  (see the graph)

My prediction for this variable was correct!  

Evaluation

From my graphs, I can see a clearer picture of the pattern I got in the results tables.  Both the line in the graph for ‘the weight of the bob’ and for ‘the angle of displacement’ vary very little.  However the points are not completely identical, and this was probably image02.png

caused by the inaccuracy of the experiment.

Every time we repeated the experiment, it

was very slightly different, therefore not

achieving the same results each time.

Nevertheless, my attempts proved similar

enough to attain these unmistakable results,

showing the obvious pattern in the results.

  It is also very obvious from looking at the other

graph that number of oscillations definetly

depended on the length of the string used.  The points on this graph make a reasonably smooth curve, only slightly incongruous where the experiment was not completely accurate (as in the other graphs).

...read more.

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