18.2 Harmonic Motion Graphs
How do we make graphs of harmonic motion?
1
Simple harmonic motion graph
Make a graph from the data table below. Draw a smooth curve that most closely shows the pattern in the data.
Answer the questions about the graph.
a.
What is the amplitude of the graph in centimeters?
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b.
2
What is the period of the graph in seconds?
Comparing harmonic motion graphs
Two different groups of students are doing experiments on giant pendulums with very long periods. Both
groups use the same clock to record time. Below are two sets of position vs. time data, one from each group.
Graph the data and answer the questions.
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a.
Which pendulum was most probably released first? In your answer you must use the word phase to
explain how you chose which pendulum started first.
b. How much time was there between the start of the lead pendulum and the start of the other pendulum?
3
A complex harmonic motion graph
Answer the three questions from this graph.
a.
What is the amplitude of the combined pendulum in centimeters?
b. What is the period of the combined pendulum in seconds?
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c.
4
In one or two sentences, describe the difference between the graphs of the single pendulums and the
graph of the combined pendulum.
How to get a complex graph
The inventor has a theory that the combined motion is the sum of the separate motions of the short and long
pendulum. The inventor measured the position versus time for the short pendulum and the long pendulum
separately. To test this theory, add up the positions for the short and long pendulums that were measured
separately. For each point in time, write the sum on the line in the table below labeled “Long plus short.”
Graph the position versus time for the combined pendulum.
a.
Does the graph confirm or disprove the inventor's theory? Explain your answer in a few sentences.
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