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What affects the time period of a pendulum.

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What affects the time period of a pendulum


I have been asked to investigate what affects the time period of 1 oscillation of a pendulum.

Definitions: Oscillation: Repeated motion of pendulum (to and for)
Period (T): Time taken for one full oscillation


I predict that the longer the length of string the longer it will take the pendulum to complete one period. This is because the length of the arc, the pendulum is traveling along is greater, but the gravitational acceleration will remain the same. This prediction is also proved by the formula


Here if the length of the string is increased (L) then that side of the equation becomes larger because the size of the fraction is increasing and because one side of the equation is increasing so must the other to remain equal so T will also increase.


What a pendulum is:

A pendulum is a body suspended by a fixed point so it can swing back and forth under the influence of gravity. Pendulums are frequently used in clocks because the interval of time for each complete oscillation, called the period, is constant.

The GPE (gravitational potential energy) gained after reaching its highest point in its swing, is converted into KE needed for it to return back to its natural point of vertical suspension. Due to this continuous motion, the bob creates an arc shaped swing.

...read more.


To make sure our results are accurate we need to keep everything but the variable constant. Below are some simple guidelines to ensure that our testing is fair.




Clamp Stand

Could rock

Place a heavy mass on the base to prevent this.

Mass of the bob (see note below)

If we use different bobs there mass could be different.

Make sure we use the same bob


Angle could be different due to human error

Make sure we measure the angle accurately


If we move to another area of the world, the effects of gravity will be slightly different

Stay in the same area of the earth as much as possible.

Human error

Human error between releasing the bob and starting the stopwatch.

Make sure the same person does each task every time, use a standard pre-release method, i.e. 3,2,1, go.  We should also let the pendulum swing for ten periods and then divide by 10 to reduce the effect of human error.

Note: Although during my research I ascertained that the mass of the bob does not effect the period of the pendulum, I should still keep this constant, as I should only have one variable in my experiment.

Note: The friction on the string caused by the air will affect the results. Ideally, this experiment would be conducted in a vacuum. However, we have no equipment in school that we could use to achieve this.

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However with the small bob with a short string it took 0.929 seconds compared to the long string which took 1.207 seconds. So obviously the length of the string affects the time. The smaller the string the bob is attached to the smaller the time it takes for a swing.

We also investigated whether the angle the ball is dropped from affects the time. With a big angle it took 12.85 secs so their was no big difference.

My prediction, based on the preliminary work is that the smaller the string the bob is attached to the smaller the time it takes for one swing. In contrast, the larger the string is, the longer the bob takes for one oscillation.

Were using a retort stand and clamp to swing the pendulum from. We will measure time for 10 ,20 ,30 ,40 , 50, 60, 70, 80, 90 7 100 cm’s length strings.

We will get 3 measurements and then average the results.

For each result we will let the pendulum swing for 10 periods and then average to eliminate human error as much as possible.

The angle will be same that we drop it from, also the weight of the bob will be the same. Were using a protractor to keep the angle the same.

We will put weights on the stand to make the results accurate.

We will not be going over 15 for the angle.

...read more.

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