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'Carry out an investigation into the factors affecting the period of a simple pendulum.'

Extracts from this document...

Introduction

GCSE Physics 2003

‘Carry out an investigation into the factors affecting

the period of a simple  pendulum.’

Part 1: Plan

Introduction:

In this investigation, I intend to determine the relationship between the length of a pendulum and the time taken for it to oscillate once. The pendulum itself will, due to limited resources, consist of a mass attached to a length of string. The weight of this mass is irrelevant for my experiment but it is, however, vital that it remains constant so that this possible variable does not alter the results obtained from the ‘length of string’ strand of investigation.

Other possible lines of enquiry:

• Angle of release
• Mass of pendulum
• Gravitational force

Theory:

The velocity of the pendulum increases as the weight falls and reaches a maximum speed at the bottom of the swing. Here, the kinetic energy is also at a maximum, and the potential energy is at a minimum. Then, as the kinetic energy causes the pendulum to continue rising, the kinetic energy is transferred back into potential energy causing the velocity of the pendulum to decrease and stop as it reaches the top of the swing, before then returning to the bottom of the period and continuing in its swing.

The unbalanced forces acting on the pendulum cause the movement and consequent oscillation in this investigation. Gravity attempts to pull the mass towards earth but is resisted by the tension in the string.

Middle

The results tabulated below were taken for each of the 3 experiments conducted using each length of rope. As can be seen, an average reading was then calculated.

11 different lengths were used in the investigation, ranging from 5cm to 55cm at intervals of 5cm.  A metre-rule was used to measure the length of each string and a stopwatch used to measure the time taken for 10 oscillations.

Data:

 time taken for 10 oscillations length (cm) test 1 (seconds) test 2 (seconds) test 3 (seconds) average (seconds) average (seconds)/10 55 17.32 17.06 17.12 17.17 1.717 50 16.28 16.29 16.4 16.32 1.632 45 15.56 15.59 15.57 15.57 1.557 40 14.66 14.69 14.66 14.67 1.467 35 13.72 13.94 13.59 13.75 1.375 30 12.69 12.71 12.65 12.68 1.268 25 11.72 11.78 11.69 11.73 1.173 20 10.47 10.53 10.59 10.53 1.053 15 9.22 9.28 9.16 9.22 0.922 10 7.44 7.63 7.54 7.54 0.754 5 5.62 5.65 5.47 5.58 0.558

Part 3: Analysis

I plotted the results obtained from the investigation on to a graph to clearly show the changes in oscillation time at each of the 11 different lengths. It is visibly apparent that, as the length of the pendulum increases, the time taken for 1 oscillation increased accordingly.

The above graph depicting

Conclusion

Factors that would need amending if further investigations were to be taken in the topic are as follows:

• More accurate method of determining pendulum length. Also less elastic string to be used.
• Begin swing of pendulum using a more precise method of release.
• Use light gates to obtain completely accurate oscillation periods and avoid any possible human error when operating stopwatches.

Possible Further Investigations:

In order to explore this topic of oscillation times and the various factors affecting them in more depth, different independent variables could be used, such as change in release angle, weight of pendulum or gravitational force. It could be that more accurate data could be obtained by using a smaller angle (15o) as this would keep a more constant time. Obviously, when investigating another variable, all other possible changes would have to remain constant for every set of experiments in order to conduct a fair and constructive experiment. In the example of ‘weight variation’, each pendulum would have a different mass attached subject while the length of rope used would have to remain constant.

Explanation:

As the length of the pendulum increases, the affect of the gravitational force on the weight when raised also increases, causing a longer oscillation time. At a smaller length the pendulum takes less time to swing 1 complete oscillation. This is because a gravitational force is acting on the weight, which forces it to counteract the force suspending the weight and cause it to swing to its original starting point.

Tom Woodgate 11T

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