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In this experiment, I chose a pound coin as the object to be measured, which I considered to be as small and heavy as possible. So it can overcome the air resistance as much as possible. For this experiment I chose a phyphox acoustic stopwatch to measure the time it takes for the coin to fall, which was calculated by using the acoustic stopwatch on my table, which is approximately 1m above the ground. Hitting the card horizontally with the ruler will not produce a vertical acceleration on the object being measured. I hit the card with the ruler parallel to the first sound, while the coin falling to the ground is the second sound, and it can be learned that the time displayed on the acoustic stopwatch is the time it takes for the coin to fall from the table to the ground, and the time for the coin to fall is 0.44s, so the result can be calculated to be 9.8 m/s² acceleration of gravity. In this experiment, the calculations are relatively accurate, but there are still some errors, the first being air resistance, which is not negligible despite the small size of the coin. The second is that sound propagation also takes time, and although this time is very short, it must be considered in this experiment. This is why the time reading on the acoustic stopwatch is on the large side.

In addition, this experiment could be improved to give more accurate results. Firstly small steel balls with less air resistance could be used instead of coins as they are spheres and therefore have less air resistance and are denser and have more buoyancy caused by the air, followed by a louder and more recognizable sound of the small steel ball falling to the ground. Secondly, by choosing a higher horizontal surface during the experiment, the effect of air resistance and speed of sound propagation can be diluted, making the results more accurate.

During this experiment, I realized that smartphones are very advanced and that there are many sensors in our common smartphones that can help us with our experiments, so it is possible to use them for scientific experiments. Besides that, this experiment has improved my thinking and design skills, which is very meaningful for my future career planning.

Smartphone Experiments Activity

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