# Physics Pendulum

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Introduction

Rebecca Chaplin - Year 10C

Mr. Eddy - Physics

THE SIMPLE PENDULUM

String

Bob Mass

Practical Investigation: The simple Pendulum

Aim: To investigate the factors which affect the period of oscillation of a simple pendulum?

Equipment: stand and clamp, pendulum bob, stopwatch, metre ruler, nylon string.

Background: The period of a pendulum is the time for one complete swing. The equation for the period of a pendulum is

Method:

- Determine the effect on the period (T) of the pendulum when the mass (m) of the bob is altered.

Set up the pendulum with a 20 cm length of string (L) so that the bob swings near a backboard. Pull the bob 6 cm to one side (the amplitude), then release it so that it swings parallel to the board. Another observer should use a stopwatch to measure the time for 20 complete swings. One swing is the time the bob takes to go out from its release position and return. Repeat this procedure using three other bobs of different masses. In each case use the same length of string and amplitude.

Enter your results in Table A.

- Determine the effect on the period of the pendulum when the amplitude is altered and the mass and the length of string are kept constant.

Middle

Table C

Mass of bob constant, amplitude of swing = 6 cm

Length of string | Time for 20 swings (sec) | Period of motion | Square root of length | |

Discussion and questions:

- Plot a graph of period (T) against length (L) and period against the square root of L. What do these graphs indicate about the relationship between period and length?

Conclusion

After experiments A, B, and C were conducted, the data obtained was recorded in tables and the square root of the length of the string, the period of motion and length of string were put into graphs.

From these graphs the gravity difference of 10.6 m/s² was worked out. Against the theoretical value our experimental value of the gravitational force was only 0.8 of a difference. This could be due to all the random and systematical errors we stated in our practical.

Through this practical report, it can be concluded that one oscillation of the pendulum is dependent on mass of the bob, the amplitude of the swing and the length of the string.

This student written piece of work is one of many that can be found in our GCSE Forces and Motion section.

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## Here's what a star student thought of this essay

### Response to the question

This is a fairly average piece, with a fair few mistakes, but overall it shows a basic understanding of the ideas of simple harmonic motion. The student has answered the question of what effects the period of oscillation of a ...

Read full review### Response to the question

This is a fairly average piece, with a fair few mistakes, but overall it shows a basic understanding of the ideas of simple harmonic motion. The student has answered the question of what effects the period of oscillation of a pendulum well, they have started off with their theory to figure out what they think will affect it and have tested to see if these do. He has also made sure to test other things that may change in a pendulum and would seem like they could affect it but theory says will not, such as the mass of the bob. He has however not read all of the questions correctly, where it says to plot the square root of length against time period he has just plotted the length. Be careful to read questions correctly.

### Level of analysis

He has managed to use theory to figure out that g can be calculated from the gradient of his graph, always make sure to think about your theory to see how you can use your results to answer the questions. On the question about errors, he has correct to say that the main error would be from the stopwatch, however the question would be backed up better if he worked out the errors for a certain value and compared the errors over his different measurements for this value to back up his decision that the stopwatch has the largest error. He has also drawn the wrong conclusion that mass affects the time period, his results indicate this but he should of noticed by calculating his errors that his results for mass all fall within each otherÃ¢â‚¬â„¢s values associated with random error. If you take errors into account you find the time period could have stayed the same. Always work out your errors to help stop mistakes like this. He should of also looked at his theory to figure out that this should not happen.

### Quality of writing

He should of followed more conventions such as using SI units of meters instead of centimetres, and kg instead of grams. He has also measured time in grams instead of seconds. He should of made sure to check over. Also to save time he could of put his units in the headings of his tables rather than after every result as he has for some but not all. This looks very messy. He has also made a table that he did not need and just left it there, it would make a lot more sense to cross it out instead of making the coursework look unfinished. His spelling and grammar however are fine. But a very important mistake that a lot of people make is shortening seconds to "sec", either keep it as seconds, or shorten to "s". This is because sec in physics is an actual measurement of angle. You'll be marked down if you put sec, harsh but true.

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Reviewed by jackhli 28/02/2012

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