Unlike many labs you may have had in other science courses, experiments in this course will not come with a detailed step-by-step manual. Instead, you will make observations and explore phenomena, design your own experiments, and make choices about how to revise and improve your work as you go along. It will take a bit of practice, so don’t get discouraged!

Today you will be working with pendulums. It’s OK if you don’t know anything about pendulums or if you haven’t seen anything about them in the lecture! Experimental physics often looks at new phenomena and you don’t need to know any underlying theory in order to do an experiment.

By the end of this lab, you will be able to…

• Collect data and revise an experimental procedure iteratively and reflectively,
• Evaluate the process and outcomes of an experiment quantitatively and qualitatively,
• Extend the scope of an investigation whether or not results come out as expected,
• Communicate the process and outcomes of an experiment, and
• Conduct an experiment collaboratively and ethically.

For this lab, we will consider the process of scientific investigation as being made up of the following five stages:

• Observation
• Hypothesis and Prediction
• Experimentation and Analysis
• Communication
• Revision

Not every lab period will include every step. Some labs will focus on one part of the process only, while others will look at the process as a whole.

In this week's lab, the TA will lead you explicitly through each of these steps.

A pendulum is any mass which – when pulled away from its starting position – will oscillate back and forth. Think of a grandfather clock or a metronome. Don't worry if you haven't yet encountered pendulums in lecture; you do not need to know any theory in order to test the model.

Today you will build a simple pendulum which has most of the mass, $m$, concentrated in a single bob at the bottom of a string of length $L$. When you pull the mass back so that the string forms an angle $\theta$ – or equivalently so that it moves out to an amplitude $A$ away from the vertical – and release it, the mass will swing back and forth, returning approximately to where it started after each cycle. The time it takes to complete a single cycle – that is, to go from one extreme to the other and back to where it started – is called the period, $T$. Equivalently, we can also measure the number of cycles that happen in a set length of time; this is the frequency of the pendulum, $f$, and it's equal to the reciprocal of the period:  $f=1/T$ .

An independent variable is a variable which you have control over. It is the variable which you can change from trial to trial.

A dependent variable is a variable which you measure. It is the variable which changes in response to your changes in the dependent variable.

A control variable is a variable which you keep fixed during an experiment. You want to make sure that all variables which are not independent or dependent are controlled, or else it may become difficult to tell what changes you are making are causing the outcome you measure.

Consider the following example:

A student wishes to measure the effectiveness of the brakes on a particular model of car. They have access to a professional driver and a closed track, as well as typical measurement tools like a stopwatch, tape measure, etc. What experiment could the student design? What would be good choices for the independent variable(s)? The dependent variable(s)? The control variable(s)?

For this lab, you will work in groups of two or three. The TA will introduce the equipment available and guide you through the lab.

Your TA will provide more details on each step, but you can consult the outline below as you progress. Remember to write down everything you see and do in your group lab notebook.

• Make sketches, do calculations, take notes, and record observations. Your TA may ask to see your notebook during lab, and will read over it afterwards.
• Use the digital group lab report to communicate the process and results from your experiment.

Remember also that you will need to share your experiment and its results with the class at the end of the period. It may be helpful to use the whiteboards to make diagrams, notes, tables, or plots of information you want to communicate to others as you go.

Consider: What happens as you change one variable and keep the others the same? In what ways can you measure your results? Can you make these measurements more accurate?

Consider: What is your independent variable? Your dependent variable? Your control variables? What is your hypothesis for this experiment and what specific prediction does it make?

Consider: What materials do you require? How will measurements be taken? By what methods are control variables being considered? What tools can be used to decrease the experimental error in the lab setup?

Consider: Do you trust your measurements? What uncertainties are present in the data and how can you quantify them? If measurements are repeated, do you get similar results?

Consider: How can you represent your results? Does any relationship exist between the variables being looked at? Are your data consistent with your prediction? Inconsistent? Inconclusive?

Consider: What do you want others to know about your experiment? How can you present your methods and results succinctly and clearly? Can you anticipate questions others might have? Can you think of improvements you’d make if you had more time?

At the end of the lab, you will need to record your final conclusions (about 1 or 2 paragraphs) in your lab report summing up the important results and take-away points from your experiment. Remember that you should only draw conclusions which are supported by the data, so be ready to back up any statements you make!

When you're finished, save your file as a PDF and submit it to the appropriate Canvas assignment. (Only one student needs to submit the notebook, but make sure everyone's name is on it!) If you make a mistake, you can re-submit, but work done after the end of the lab period will not be accepted.