Physics One presents a novel approach to freshman laboratory experiments. There is no fancy electronic apparatus, and no detailed instructions on exactly what to do and how to do it. Instead students are shown how to develop e.g., the most accurate method for measuring the period of a pendulum, and how to know that it is the most accurate method that they found. The introduction to the experimental part of the book appears in this link.
A Sequence of Experiments
In Part I of the course, we present a theoretical treatment of classical mechanics. Physics theory was the work of a number of great physicists, included Isaac Newton, James Clerk Maxwell, Josiah Willard Gibbs, Albert Einstein, Erwin Schroedinger, Werner Karl Heisenberg, Paul Adrien Maurice Dirac, and moderns too numerous to mention. There is also experiment, in which we study nature to see how it behaves. We’ve already mentioned Tycho Brahe, Chien-Shiung Wu, and Rainer Weiss, but there are a vast number of other people who did important experiments.
All these theorists and experimenters when successful generate new results. Newton presented his results, his Laws of Motion, by writing a book, but under modern circumstances results are reported to the scientific world in the form of short papers (typically 4-20 pages) in scientific journals. There are then a very few people whose specialty is reading all those papers, summarizing them, and presenting them to the scientific world in the form of review articles (indeed, there is a journal, Reviews of Modern Physics, that only publishes these review articles). As we have mentioned great theorists, and great experimentalists, it would only do to mention a great reviewer, Virginia Louise Trimble, whose reviews on the Solar neutrino problem forced recognition that there was indeed a problem.
The purpose of this experimental sequence is to give you some experience in doing real experiments. A real experiment is an experiment in which you do not know the answer in advance. Real experimental work has important parts that are not often discussed in physics courses. These experiments will introduce you to some of those parts. I therefore do not give detailed instructions as to exactly how to do your experiments. Indeed, an important part of experimental work is to realize that there may well be several different methods of measuring the same quantity, and that experiment may be needed in order to determine which experimental approach gives the best results. Real experiments have errors, some of whose sizes can be determined experimentally.
These experiments are very much not like the experiments you will encounter in some freshman physics courses, where the objective is to confirm with experiment that I was telling the truth about, e.g., the period of a pendulum, and if your experiment fails to confirm theory, you are required to go back to the lab and do the experiment again and again until it confirms the theory. (No, I did not make that up.) The experiments here are meant to show you, with very little equipment and some basic mechanics, how you would go about designing an experiment. Yes, the results are known in advance, but that’s not the point of what you are doing.
You may have been told about a scientific method in which the sole purpose of an experiment is to test a hypothesis. In this method, before you do an experiment, you are required to make a guess (a hypothesis) as to the correct answer. The objective of the experiment is to determine if your guess is true or false. If the experiment disagrees with your guess, your guess is wrong and must be rejected. That approach to science is not always correct. You may find it interesting to read a history of the solar neutrino problem, in which measurements of solar neutrino emissions were made, two-thirds of the neutrinos were missing, and the neutrino instrumentation, solar modeling, and nuclear physics people could each think the fault was not theirs.
Much real science does not resemble this supposed `scientific method’. For example, when the United States set out to sequence the human genome, it was already extremely well established that homo sapiens had chromosomes with DNA sequences. In principle, you could have guessed the DNA sequence, and then done experiments to see if your guess was right. However, the number of possible human DNA sequences is somewhat large, say four to the 3.2 billion power, so the likelihood that any guess would be correct is exceedingly small. What was actually done was exploratory. We did not know what was there, so we set out to measure it. That’s real science.
These laboratories will require a very modest amount of equipment. You are going to study a conventional pendulum, a physical pendulum, and an Atwood machine.