line drawing of pendulum motion for Swinging Science
Student Guide

Swinging Science

Experimenting with forces and variables of swinging objects.

What variables affect the period of a swinging object?

This resource was originally published in PhysicsQuest 2020: Force & Motion.

What variables affect the period of a swinging object?

  • 2 lengths strings
  • 4 hex nuts
  • A ruler or measuring tape (optional)
  • A timer (optional)
  • Sheets of graph paper (optional)
Intro

Most people enjoy going to playgrounds and playing on the swings. But did you know that the movement of swings—or pendulums—is one of the most studied problems in physics? Understanding their movement has helped people tell time, keep the beat or rhythm in music, and protect buildings against earthquakes. Do you know what causes a swing to move back and forth if you only raise it and release it? There are many variables that affect how a pendulum swings. In this experiment, students will learn what some of these variables are and design experiments to test them.

After reading the introduction, what is your essential question or objective for this activity?

Before the experiment

  • What is your role in your group? Define your job expectations.

  • What variables do you think affects the pendulum's swing?

  • Of the variables you could think of, which ones you would classify as independent variables (variables you change) and which ones you would classify as dependent variables (variables you measure after changing an independent variable)?

  • If you were to change your independent variable, what do you think will happen? Write a hypothesis.

Setting up

  • Attach the nuts to the lengths of string.

  • Place the ruler on a flat surface and hold the string and nut above the ruler.

  • Measure how far back you pull the nut before you let it go.

  • Measure the period.

  • Record your results.

During the experiment
Collecting data

  • List ways you might be able to change the variables with the materials you have in front of you.

  • Draw a labeled sketch or write the process of your experiment to test one of the variables.

  • What materials do you need to measure your variables?

  • What variables are present in your experiment and how are you controlling for them?

  • Work with your group to collect data from the experiment you designed. Write down the results each time you repeat it. Write your observations below.

  • What was the result of the experiment?

  • Did you get the same result every time? Why do you think that is?

Analyzing data

  • Make a table where you have the values for your independent variable in one column and the corresponding values for the dependent variable in the other. For example, if you want to see how the pendulum movement changes when you change the length, then the period (the time it takes the pendulum to swing one way and back) should be on the dependent variable column, while the length of the string should be on the next column, as the independent variable. Take several measurements with the same length before you test a new length. Do you notice any patterns?

  • Try graphing your data. Remember, the independent variable always goes on the x-axis and the dependent variable goes on the y-axis. Do you see any patterns now?

  • Gather data from all groups that tested different independent variables.

Conclusion

  • How does a pendulum swing, and what affects its movement?

  • Use your graph to explain what variables affect the period of a swinging object.

  • How did you think you did at your group job? What were your strengths in this role? What do you want to improve upon for next time?

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