# The Science of Spin: A Baseball Pendulum *

 Difficulty Time Required Short (2-5 days)
*Note: This is an abbreviated Project Idea, without notes to start your background research, a specific list of materials, or a procedure for how to do the experiment. You can identify abbreviated Project Ideas by the asterisk at the end of the title. If you want a Project Idea with full instructions, please pick one without an asterisk.

## Abstract

For this project, you'll use a baseball as a pendulum weight, studying the motion of the ball with and without spin. Wrap a rubber band around the ball, and tie a string to the rubber band. Fasten the string so that the ball hangs down and can swing freely. Mark a regular grid on cardboard, and place it directly beneath the ball to measure the motion. You can also time the oscillations with a stopwatch. Lift the ball along one of the grid axes, and let it go. Observe the motion and record your results. Next, twist the string 50β100 times, and again lift the ball along one of the grid lines and let it go. How does spinning change the motion of the pendulum? Try changing the orientation of the seams of the ball: is the pendulum motion affected? What happens if you wind the string in the opposite direction? Can your results help you explain how a pitcher throws a curve ball? (Idea from Goodstein, 1999, pp. 50β53. Adair, 2002, has an extensive treatment of baseball aerodynamics.)

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Last edit date: 2013-01-10

## Bibliography

• Adair, Robert K. The Physics of Baseball: Third Edition, Revised, Updated and Expanded. New York: HarperCollins Publishers, 2002.
• Goodstein, Madeline. Sports Science Projects: The Physics of Balls in Motion. Berkeley Heights, NJ: Enslow Publishers, 1999.

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