The aim of my experiment is to investigate whether the change of length of the string is proportional to the time of a swing of a simple pendulum.
A simple pendulum can be defined s an object which is suspended by a light, inextensible thread from a fixed point, allowing the pendulum to oscillate. The time required for one complete oscillation is known as the period of a pendulum (T). Time of a swing of a pendulum is affected by the length of the thread and the angle that the pendulum is released at.
I predict that the increase in the length will lead to increase in the time it takes the ball to swing. This occurs because the by increasing the length of thread you are increasing the arc, that the ball has to travel along.
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Time of a swing of the pendulum is proportional to the square root of length.
In this experiment I will use 3 stopwatches, a protractor, a stand, a lead ball, a 1m ruler, a clamp and 100cm thread. The experiment is setup as follows:
- Prepare the materials needed.
- Setup a pendulum as shown in the diagram.
- Raise the string to 90° and release it while timing.
- Stop the timer after 4 complete oscillations are achieved.
- Average and record the timing.
- Change the length of the rope according to guidelines below.
- Repeat the process 10 times.
My variable is the length of the thread. We will vary the length of the tread by 5cm. We will start with a thread 10cm long and will gradually build up: 10, 15, 20 cm and so on.
I will ensure that the practical work that I do is safe by wearing safety goggles, putting the apparatus behind a safety screen and by gently releasing the ball.
I will make sure the experiment is fair by ensuring that the lengths are kept accurate, the release point stays the same and make sure that the ball is released, not pushed.
I will keep my results accurate by having the swings timed by 3 people and then producing an average.
From my graph I can see that the general trend is positive. When the length of pendulum’s thread is 10cm the time for one swing is 0.395sec, when the length of the thread is 20cm the time for one swing is 0.4716sec. This shows us that the time for one swing increases as the length of the thread increases. This shows us that my prediction was correct. The clear explanation of why this is happening is based in my prediction.
I found this experiment difficult because it was very hard to time the swing of the pendulum as no one knew exactly where the pendulum achieved a full swing. I could improve the experiment next time by using some kind of a more accurate instrument to measure the time.
My experiment was accurate because 3 people timed the swings giving us a result which we then averaged to achieve higher accuracy. My experiment was not accurate because the metal rod might have not been stable, thus affecting the time for the swing, the measurement of the length of the string may have not been accurate since the length of the string is extended to the centre of the bob, the time was always slightly off because no one could exactly tell where the pendulum has achieved its swing. The experiment could be made accurate by using more sensitive equipment to time the swing.
There may be an odd result at 75 cm; this may be because the timing is not accurate.
I could further my investigation by doing more different lengths to achieve more accurate results.