Investigating Pendulums: An exercise in the scientific method

A Pendulum is a simple device consisting of a hanging string attached to a weight in such a way so that the weight is free to swing. Galileo started thinking about pendulums as he sat in church and watched a large chandelier swing back and forth. Since watches had not been invented yet, he used his pulse rate as a way of measuring the motion of the chandelier (pendulum). He soon started doing scientific investigations to answer the questions, which his observations stimulated. By observing your own pendulum and writing down questions that occur to you, you will be following Galileo’s example in using the Scientific Method. Unlike Galileo, you have a number of modern tools that will help your investigation, don’t forget to use them:

  • Stopwatch
  • Meter stick
  • Metric balance

The lab report for this investigation will consist of everything you are asked to do in this lab packet. It should be typed and numbered by the number of each step and each step should have an appropriate title. THE CLOSER YOU FOLLOW THE DIRECTIONS OF THIS HAND OUT THE BETTER YOUR PRODUCT WILL BE. ASK IF YOU ARE NOT SURE WHAT TO DO.

  1. Look at the demonstration pendulum at the front of the room.

Make a sketch of the apparatus and label each part

  1. Set up your own pendulum. The weight at the lower end is called the pendulum bob. The pendulum should be 30cm long, counting the length of the bob. Make a list of five observations and measurements, which describe the pendulum and its motion. You should use the tools that are available to help you. You can use the stopwatch or your own wristwatch, to time the period of the pendulum. The period is the length of time it takes to make a full back and forth swing or oscillation.
  1. It is natural for humans to be curious about what they observe. As you observe your pendulum, questions should arise in your mind about what you see. Write down your questions about the pendulum and its motion. There should be at least three questions, but the more the better. Good questions are those, which can be answered by experiment. We will discuss these questions as a class and decide which ones will make a good basis for further investigations.
  1. Scientists can discover the answer to some of their questions by using the scientific method. After observing a phenomenon like the pendulum and asking a question about it, a temporary answer, an “educated guess” based on past experience (an hypothesis) can be given. A good hypothesis is one, which can be tested by doing an experiment. Write down the question you are going to investigate and the hypothesis that you have about it.
  2. The next step is to decide on a way to test your hypothesis. You do this by designing an activity, called an experiment, which will give you data that helps you decide on the validity of you hypothesis. You will work with your partner and teacher to come up with an appropriate design. Write down the steps of the procedure and a list of the materials to be used. Remember that your procedure must produce data for a line graph.
  1. After consulting with your teacher, do your experiment and collect the data. You should produce a data table.
  1. Answer the following questions based on your data:
  2. Draw a line graph of your data and write a sentence describing what it shows.
  3. Discuss in detail what you have learned about the motion of a pendulum based on your observations, experiments and data
  4. State whether the data supports your hypothesis, or rejects it.
  5. Write down your conclusion. The conclusion should address your original question.