Can the magnitude of gravity be found by measuring the period in relation to the length of the string of an oscillating pendulum?

The aim with this lab was for us to gain a greater understanding in the area of oscillations and simple harmonic motion. Also to determine if the use of a pendulum is a good strategy for measuring the gravity.

I found this experiment to be very interesting since I’ve seen and used pendulums a lot before, but I have never really reflected on why they oscillate. After this lab and understanding of the theory, I even know how to relate measurements to figure out the force of gravity. That is why I love physics, everything is related which makes it possible to explain phenomena seen in the everyday life.

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The weight of 100 grams was the controlled variable which means that it was held constant during the entire experiment. The mass was connected to the string which represents the independent variable since we varied the length of the string throughout the lab. We tied a loop on the string to hang it on the clamp so the weight was free to move. The string was very lightweight compared to the mass due to being able to come as close to the ideal of a massless string as possible.

The dependent variable was the period of the pendulum. The weight was put in motion with a fairly small force so the pendulum was able to oscillate with a small angle. We decided to measure 10 full periods in the sake of accuracy, then divide the result by ten to get the measure for exactly one period. The stop watch should be started at the highest point where the weight contains no kinetic energy, just potential energy, and stopped at the identical spot. Repeated measurements should be performed to reduce the risk of errors.

RESULT

Table 1. The raw data contains information about the time taken for the pendulum to complete 10 full

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To get a result as close to the ideal model as possible, the angle from the equilibrium point to the maxima should be significant small. So small that the amplitude, which has the shape of an arc, could be assumed to be a straight line. In that case, the oscillations could be treated as simple harmonic motion and the calculations would be able to give a realistic result. The period is obviously affected by the angle as well, since it takes longer time to complete one period if the angle is greater. As seen in table 1, our raw data has a fairly big spread even though the length of the string is constant, which is a result of different angles. A protractor could have been used to ensure accuracy and controlled