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This week's LabZone activity
Jan. 11, 2006
The Pendulum
Nearly all of the great astronomers made contributions to physics and other sciences. In order to advance their astronomical studies, they had to understand many scientific principles, including gravity and acceleration (increase in speed). Galileo was one of the first scientists to experiment with the properties of the pendulum. He noticed that the period (the amount of time it took for the pendulum to go back and forth once) of a pendulum's swing is related only to the length of the pendulum's rope. The amount of weight attached or the amplitude of swing (how high and far the pendulum swings) does not matter.
Observe for yourself what Galileo first saw more than 400 years ago.
Materials
- Scissors
- Long length (at least 3 feet [1 meter] of thin string (for example, the type used in bakeries)
- 3 weights of different sizes (all of which should be easily attachable to the string)
- Plant hook, flagpole, or other hook that will allow a string with weight to hang unobstructed
- Stopwatch or digital timer that shows seconds
Cut the string into three different lengths (6 inches [15 cm], 12 inches [30 cm], and 18 inches [45 cm]). Attach a weight to one of the strings and hang the string from the hook. Using the stopwatch, time how long it takes for one complete swing (back and forth), pulling the weight to different heights along the arc before releasing it. Now, change weights and time it again. When you have used all the different weights, switch strings and try again using the three different weights. Each string should give you the same period of time, no matter what the weight or amplitude (range) of swing.
Reprinted with permission from Galileo for Kids: His Life and Ideas, 25 Activities by Richard Panchyk. Published by Chicago Review Press, distributed by Independent Publishers Group (www.ipgbook.com). Copyright © 2005 by Richard Panchyk.
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