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Introduction

Investigating a factor which can affect the period of a pendulum PLAN Aim: I am going to investigate the relationship between the length of a pendulum and the time for one oscillation to occur. Factors which affect the period of a pendulum: -length of a pendulum -angle of altitude of a pendulum -weight of bob of a pendulum -gravitational field strength surrounding pendulum The type of pendulum that is going to be used in this experiment is a simple pendulum which consists of a small mass (bob) suspended by light, inextensible thread of length (l) from a fixed point. If the bob is drawn aside and released, it will oscillate to and fro in a vertical plane along the arc of a circle. Variables: What will be altered or kept the same during the experiment. Variables table: Dependent variable Value How value will be measured 1 Period time for 10 oscillations � 10 digital stop clock 3 repeats for each length Independent variable Length 0.1 to 0.8 metres with 10cm intervals meter ruler Controlled variables Size of swing 30� protractor Mass of bob 500g 5 x 100g weights gravity 10N/kg Prediction: I predict that the length of the pendulum will have an effect on the period . The longer the length of the pendulum, the longer the period. This is because, based on a theory I found in an A Level text book, the pendulum is able to work when its bob is suspended at a higher angle than the one it is when at rest, vertically suspended. ...read more.

Middle

Precise uses of measurement will be used to ensure that the variables change/remaine constant during the experiment: -Using a metre ruler to measure the pendulum's length. -Using a protractor to measure the pendulum's angle of altitude -Using a stop clock to measure the pendulum's period(s) to 2 decimal places of a second. -Using 5 x 100g masses to measure the pendulum's bob of 500g. Not many safety risks were involved, although the following should be considered to provide a safe test: -The angle of altitude was kept to a minimum of 30� to avoid large swings leading the bob to come into contact with anything and causing damage. Preliminary work: We researched our investigation before carrying out the experiment by looking at theories and equations in A level Physics text books. We also carried out a very short experiment with a pendulum of length 20cm and of 50cm to see if there was a big enough difference to get varied results for the more detailed experiment. Fair test: To ensure accurate and reliable results, the following will be considered: -So that the velocity of the swing is not affected, we will make sure that there are no obstructions to the swing of the pendulum. -The interval between the string's length will increase by only 10cm each time; this will help prove a clear pattern in the results. -The angle of altitude will remain as 30� throughout, ensuring there is no change in the forces acting upon the pendulum. ...read more.

Conclusion

Excluding human error, the procedure and formula exercised were regarded as reliable and so, I can support that my evidence concludes that one factor that affects the period of a simple pendulum is its length. When the length increases, the period increases; when the length decreases, the period decreases. The procedure and formula exercised was understandable and straightforward; however certain improvements could be made to make results more efficient by being more reliable. More repeats could have been applied to the method to obtain a more specific average. The pendulum's length was in the form of string, as a result of having 500g suspended on it, the string could have accumulated extra length by being stretched; this could have been improved by using stronger, more rigid material as the pendulum's length. When measuring the length of a pendulum, instead of guessing where the end of the bob is against the metre ruler, the ruler could have been placed level with the point of suspension and a set square placed along it, touching the bottom of the pendulum to improve accurate readings. To extend this investigation, I would further explore the relationship between mass and/or angle of altitude and a pendulum's period. Also, how the pendulum differs when its factors are affected by a different gravitational field strength, not 9.8 Newtons per kg. All these different relationships would help provide a deeper understanding of factors that affect a pendulum and so, I would be able to provide additional evidence to support my conclusion and scientific theory. ...read more.

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