Your Physics Labs are a Disgrace

Physics teacher Thomas Strasser explains why Stuyvesant Physics labs are counter-effective and based on bad science.

Reading Time: 4 minutes

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By Zoe Oppenheimer

Physics is an experimental science, and physics labs should teach you experimental physics. You should learn how to plan experiments, how to conduct and evaluate them. You should learn to decide how many measurements you need and to conclude when you have enough data. You should learn how to best visualize your results and how to extract the most information from your graphs. You should learn to judge how reliable your measurement results are and how to evaluate when results differ significantly from each other. You should learn to improve your experiments based on a thorough analysis of your results. In short, you should learn what physicists do in an experiment.

Unfortunately, you do not learn this at Stuyvesant. Instead, you have to work your way through a set of prescribed procedures: you are told in great detail how experiments are set up, which measurements should be taken, how many data points are needed, which data points are to be used, how results have to be plotted, and even which calculations should be used to get results.

Do you think a physicist goes into her lab in the morning and opens a booklet that tells her every step of what she is supposed to do? Of course not. This is not how physics works, and it should not be the way physics labs are set up. Physics education research clearly shows that labs should focus on teaching experimental skills¹, and that is pretty much the opposite of what Stuyvesant is offering you.

AP Physics 1 should have a strong lab focus; in fact, the AP Physics 1 exam specifically includes an experimental design question. Stuyvesant is not preparing you for this properly. Even though the physics class this year is AP Physics 1, the Administration has just given you the exact same labs that students did in double periods for Regents physics last year. They did not modify the labs in any way to adjust them to single periods or make them align with the AP Physics lab requirements; a third of your labs do not even cover AP Physics 1 topics.

Modern experimental physics relies heavily on computers, and physics labs in the 21st century should teach you how to utilize computers for data analysis. At Stuyvesant, we make you work with homemade, half-broken equipment straight from the 1970s. It’s not that we don’t have modern equipment—we just don’t use it: last year, the Administration discarded boxes full of 20-year-old computer sensors that were never used. Most of these sensors were still in their original packaging, but they had grown obsolete in their two decades on the shelf, and did not work with modern computers. Stuyvesant purchased brand new sensors again last year. Why didn’t you get to use them? Why did you have to work with decade-old ticker tape machines and warped inclined planes instead?

And as if this were not bad enough, your labs have the science wrong for key parts of the curriculum. Your lab booklet consistently misuses percent error as if it were an indicator of the quality of your result. If you are a scientist and you are the first person to measure a quantity, what would you use as the “expected” value? There is none—you are measuring this quantity for the first time. Still, scientists can express the quality of a measurement, and they use the concept of uncertainty to do so².

If you are currently taking physics, let me illustrate with Lab 2, where you analyzed the ticker tape to find the acceleration of gravity. With the ruler you used, any measurement of the acceleration of gravity will have an uncertainty of about 3ms2. When I tried doing the lab, I measured it to be 7.5ms2±3ms2. That means that I can be certain that the “real” value for the acceleration of gravity is in the range from 4.5ms2 to 10.5ms2. If you were to measure 9.5ms2±3ms2, would your result be better than mine? No—both measurements would have the same uncertainty and both uncertainty ranges would include the value that scientists have measured many times before us. The huge range of uncertainty just means that this ticker tape method is a terrible way to measure the acceleration of gravity. I measured the acceleration of gravity with a simple pendulum as 9.86ms2±0.07ms2 with about the same amount of time and effort—a much better method and a much better result.

What is really outrageous is that some lab classes take this abuse of science even further and require you to have a percent error of less than 10 percent; a measurement of 9.5ms2±3ms2 and a measurement of 7.5ms2±3ms2 are completely equivalent in quality (equally bad, if you like) and the fact that 9.5ms2±3ms2 is closer to the “expected value” is a matter of pure luck.

But what would you do if your lab teacher required you to be within 10 percent error and you were not lucky enough to fall in that range? You could only cheat and make up fake data, claiming that you had less than a 10 percent error when in fact you hadn’t. My measurement of 7.5ms2±3ms2 would not have been accepted in these lab classes either, and I would have had to resort to cheating as well.

The physics labs at Stuyvesant would be embarrassing for any high school, let alone for one that claims to have a science focus. Their formulaic approach doesn’t foster scientific thinking and creativity. They meet neither the time nor the quality requirements for AP Physics 1 labs, and they use obsolete technology even though we have better equipment that we don’t use. I and many other physics teachers have complained about the appalling quality of the physics labs to the administration many times to no effect. This administration ignores us teachers, but they might listen to you; let the administration know if you are not happy with your Physics labs. Tell them if you would like to work with modern equipment. If you don’t like being forced to cheat, complain.

You deserve better—just ask for it.

¹N. G. Holmes, C. Wieman, Physics Today 71, 1, 38 (2018).
View online: https://doi.org/10.1063/PT.3.3816

²"Any measurement that you make without the knowledge of its uncertainty is completely meaningless." Professor Walter Lewin, Lectures on physics
View online: https://youtu.be/GtOGurrUPmQ?t=279

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