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Lab Report for Physics Lab...

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Playable Wine Glasses Benjamin Dinh Experiment carried out on: May 10th, 2020 Portland State University PHY 216-R3 Instructor: Cristal Vann June 4th, 2020 Introduction While volume of a liquid plays a major role in the pitch and frequency that it omits, another variable that must be taken into account is the liquid’s density. With this in mind, I conducted an experiment to investigate the role in which density plays in a liquid’s pitch/frequency. This phenomenon relates to the physics world in that it investigates frequency and pitch, falling under the study of waves. As we have conducted in recent labs during this term, we have observed from one experiment that the density of a string does indeed affect its frequency, when oscillated, and to observe any changes, we measured the nodes and antinodes of the waves created. This then led to me hypothesizing, In choosing to use wine glasses and

 y various liquids as instruments, the more dense a liquid is, the higher the pitch it will omit. M main object was to investigate whether my collected data supports the hypothesis. Prior to beginning the experiment, a selection of four liquids were to be selected. In this case, I chose to use Milk, Water, Cranberry Juice, and Margarita Cocktail. In selecting these four liquids, I would place approximately 6.5 ounces or 192 mL of each liquid in different wine glasses of the same volume. Following this, I would then use a stick of 7 inches in length to strike the top of each wine glass, and use the software Google Science Journal App to measure the pitch omitted when each wine glass was striked. I would then conduct three tests per each

liquid, and fill out Table 1-1 below. Proceeding this, I plotted a graph of Density v.s. Average Pitch of each liquid to see if there was indeed a correlation that would indicate a relationship. In order to measure the density of each liquid, I measured out on a scale the weight of each liquid when it was at 192 mL, and divided its mass over volume to calculate density. In Figure 1-1 below, is the experimental apparatus setup, and Figure 1-2 is a screenshot of the software used during this experiment.

Figure 1-1

Figure 1-2

Data and Analysis Table 1-1 Liquid

Volume (mL)

Mass (g)

Pitch (hz)

Milk #1

192

190

2460.8

Milk #2

192

190

2455.8

Milk #3

192

190

2455.6 kg

Density: 989.58 m3

Avg. Pitch: 2457.4

Cranberry Juice #1

192

183

2629.4

Cranberry Juice #2

192

183

2629.7

Cranberry Juice #3

192

183

2627.4 kg

Density: 953.13 m3

Avg. Pitch: 2628.8

Water #1

192

186

2602.8

Water #2

192

186

2603.5

Water #3

192

186

2604.8 kg

Density: 968.75 m3

Avg. Pitch: 2603.7

Margarita Cocktail #1

192

174

1314.5

Margarita Cocktail #2

192

174

1315.6

Margarita Cocktail #3

192

174

1313.8 kg

Density: 906.25 m3

Graph 1-1

Avg. Pitch: 1314.6

By looking at the data points from the chart plotted on in Graph 1-1, we can see that generally that the higher the density was of a liquid, the higher its pitch tended to be. Although, based off the graph, we can see that some of the points seem to not be in agreement with the other points and fit well with the line of best fit. The trendline seems to be linear, which is a good indication, but there could be room for improvement due to some points being outliers, and not being accurate to other points. To further prove and deem this experiment to be accurate, I researched in hopes of finding an equation that would help relate density with frequency, but could not find one that would relate between a liquid’s density and frequency. This made it difficult to find a theoretical value to compare to my experimental value and produce a percent error. I do believe that there was an error that occurred during the duration of the experiment, and although I had conducted each liquid’s test 3 times, I believe that it may have been that the measurement tools that I had provided in my home were not sufficient enough to produce accurate and precise data. This is only one error that I believe could have occurred. Another error that I believed could have led to

skewed data would be simply that I could not perform this experiment in a lab setting and run more trials. If given the opportunity to run this experiment once more, I would love to do so in a lab setting with the appropriate tools and collaborate with a TA or professor in hopes of finding an equation that would help me identify the theoretical value.

Discussion, Conclusion, and Personal Reflections Overall, this experiment helped my understanding of how a liquid’s density affects its frequency. As seen from the data, my hypothesis is supported to a certain extent, but is nowhere near the conclusion that it is fully supported. Just based on the experiment, I could accept that my initial hypothesis is more confident due to my data collected. My understanding from the first lab, that explained the standing waves on a string, helped me to conduct this experiment in a successful manner. By understanding that there is indeed a relationship between the density of an object and its frequency, I can have a general idea of how that may be applied to a liquid's density. I learned and gathered the abilities to conduct this experiment in a way that could be repeated in the future, with hopes of better results with a lower chance of error. From the initial experiment that I had intended to conduct, I would be varying the liquid’s volumes, and I found that this would be fairly difficult to understand if I were to also be varying the types of liquids used. This led me to simplify my experiment so that I would only be testing how the densities affected the pitch/frequency. If I had the opportunity to conduct this experiment again, I would repeat the same steps, but research more to understand an equation that would help to support my data and hypothesis....