# Playing the Angles: The Physics of Balls Bouncing Off of Surfaces *

 Areas of Science Sports Science Difficulty Time Required Long (2-4 weeks)
*Note: For this science project you will need to develop your own experimental procedure. Use the information in the summary tab as a starting place. If you would like to discuss your ideas or need help troubleshooting, use the Ask An Expert forum. Our Experts won't do the work for you, but they will make suggestions and offer guidance if you come to them with specific questions.

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## Abstract

Think of hitting a baseball, heading a soccer ball into the net, or hitting a tennis ball with a racquet. Where the ball goes depends on...what? You can set up a simple model to start your investigation. You'll need a marble, a flat piece of wood, a flat piece of cardboard, a pencil, a ruler, a protractor, and a level surface. Lay down the cardboard down on a level surface and set up the flat piece of wood at one edge. The wood will act like a wall, and you're going to roll the marble at it from different angles to see how the marble bounces off. On the cardboard, mark the starting point, the point where the marble strikes the wood, and a point along the marble's path as it rolls away from the wood. Use the pencil and ruler to connect the incoming and outgoing trajectories of the marble to the point where the marble bounced off the wood. Draw a line perpendicular to this point, and measure the angle between the perpendicular line and the incoming and outgoing trajectories. Do this for at least 10 trials at each of several different angles. What is the relationship between the two angles? Now apply what you learned to a real-life sports situation (like heading a soccer ball or hitting a baseball). In the real-life situation, the ball is no longer hitting a stationary target and bouncing off, it's hitting something that is moving. That makes it harder to measure the angles; just remember that what is important is measuring the angles at the point of impact. For a more advanced project, you may also want to consider how the spin of the ball can change its trajectory. You could choose to concentrate only on the spin imparted by the kick, the bat or the racquet, or you may want to get really complicated and consider the spin of the incoming ball as well. (Idea from Wiese, 2002, 31-34.)

## Bibliography

Wiese, J., 2002. Sports Science: 40 Goal-Scoring, High-Flying, Medal-Winning Experiments for Kids. New York, NY: John Wiley and Sons.

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### MLA Style

Science Buddies Staff. "Playing the Angles: The Physics of Balls Bouncing Off of Surfaces." Science Buddies, 28 July 2017, https://www.sciencebuddies.org/science-fair-projects/project-ideas/Sports_p040/sports-science/physics-ball-bounce?from=Blog. Accessed 30 Sep. 2020.

### APA Style

Science Buddies Staff. (2017, July 28). Playing the Angles: The Physics of Balls Bouncing Off of Surfaces. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/Sports_p040/sports-science/physics-ball-bounce?from=Blog

Last edit date: 2017-07-28

## Experimental Procedure

For this science project you will need to develop your own experimental procedure. Use the information in the summary tab as a starting place. If you would like to discuss your ideas or need help troubleshooting, use the Ask An Expert forum. Our Experts won't do the work for you, but they will make suggestions and offer guidance if you come to them with specific questions.

If you want a Project Idea with full instructions, please pick one without an asterisk (*) at the end of the title.

## Share your story with Science Buddies!

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

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