Nothing But Net: The Science of Shooting Hoops

Objective

The goal of this project is to determine if the ball's starting position for shooting a basketball affects a player's shooting percentage. In this project, you'll measure shooting percentage when players shoot baskets from chest height, chin height, and over the head.

Introduction

Click here to watch a video of this investigation, produced by DragonflyTV and presented by pbskidsgo.org

If you're an avid basketball player, then few things are more satisfying than sinking a perfect jump shot, hitting nothing but net. What goes into making that perfect shot? What can you do to make your shots more accurate?

Jay and Jonathan both like basketball, and they're also pretty observant. They noticed that some kids liked to shoot from chest height, others from chin height, and others from over their heads. They wondered what effect the different starting positions had on shooting success. They set up an experiment to find out. Check out the video clip at right to see what they did.

Jay and Jonathan took a great approach to their project. Starting with a subject they knew and liked, they used observations about shooting styles to come up with an interesting question: does the height where the player holds the ball affect shooting percentage? They designed an experiment to test their hypothesis, keeping all experimental conditions constant, except for the variable of interest. Jay and Jonathan also did a great job with their data analysis. When their data disproved their initial hypothesis, they didn't stop. They dug deeper to see if their data might hold some other clue for shooting success.

If you've read this far, it's a good bet you're thinking about doing a basketball-related project, too. You could repeat Jay and Jonathan's experiment yourself. We've suggested a couple of improvements in the Experimental Procedure section below, and you can probably come up with some of your own. Or, you could use your powers of observation to come up with your own basketball question to test scientifically. The Variations section also has some ideas that might help you get started.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• arc,
• trajectory,
• backspin,
• basketball shooting percentage.

More advanced students should also study:

• physics of projectile motion.

Questions

• Which trajectory do you think improves your chance of making a basket: higher or lower? Explain why.
• Do you think that there will be a relationship between the ball's starting position (chest height, chin height, or over the head) and the ball's trajectory? Why or why not?

Bibliography

• TPT, 2006. "Basketball by Jay and Jonathan," DragonflyTV, Twin Cities Public Television http://pbskids.org/dragonflytv/show/basketball.html.
• Cull, T., 1999. "Why is putting rotation on a basketball when you shoot good?" MadSci Network: Physics [accessed June 15, 2006] http://www.madsci.org/posts/archives/jun99/929552614.Ph.r.html.
• Henderson, T., 2004. "Lesson 2: Projectile Motion," The Physics Classroom, Glenbrook South High School, Glenview, IL [accessed June 15, 2006] http://gbs.glenbrook.k12.il.us/Academics/gbssci/phys/Class/vectors/u3l2a.html.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

• basketball,
• basketball court, hoop, and backboard,
• volunteer players to shoot baskets (the more the better),
• masking tape.

The following items are optional, but can give you a better understanding of what is going on with the different hand positions.

video camera and tripod to record the shots,

small TV or video monitor for camera playback,

transparencies,

marker or stickers to mark ball position,

protractor for measuring launch angle.

Experimental Procedure

1. Pick a single location on the court for all players to shoot from, and mark it with masking tape. Choose the location so that your volunteers can make a good percentage of their shots. A straight-on shot would be a good choice, e.g., from the middle of the free-throw line. If your volunteers are younger players, you may want to move the shooting location in closer.
2. If you have a video camera, set it up on a tripod to record the shots. Make sure that the camera can capture the ball all the way from the player's hands to the basket. The camera should be perpendicular to the path of the ball. The camera should remain in the same position for the entire experiment.
3. Have each player shoot the same number of baskets from each hand position (chest height, chin height, and over the head). Things to think about:
   1. How many shots? You want to collect a large enough sample so that your results are reliable. Ten shots per hand position per player is a bare minimum.
   2. You might want to let each player take a few "warm-up" shots that don't count, so that they can home in on the right distance.
   3. Along that same line, since the players are getting practice as they go along, it would be a good idea to change the order of the hand positions from player to player. Have the first player shoot chest high, then chin high, then over the head. Have the second player shoot chin high, then over the head, then chest high. Have the third player shoot over the head, then chest high, then chin high. Keep rotating through the hand positions like this, so that each hand position is first, second, or third equally often.
   4. To help keep everyone's mind on doing their best, you might want to make a contest out of it. For example, you could offer prizes for the top three shooters, or for all the players who make a certain percentage of their shots.
4. Keep track of how many shots each player made from each hand position. Keep track of the order you assigned them for making the shots.

   Analyze Your Data

5. Calculate the shooting percentage for each individual for each hand position. Make a bar graph of the results. Is any position clearly better for all players? Is any position clearly better for individual players?
6. Did the players' shooting percentage improve or worsen during the experiment? Make symbol-and-line graph of shooting percentage vs. 1st, 2nd, and 3rd hand position to find out.
7. If you were able to videotape the experiments, you can analyze the trajectory of the ball, as Jay and Jonathan did in the video clip in the Introduction.
   1. Connect the video camera to a small TV or video monitor for playback.
   2. For each shot you analyze, tape a transparency over the monitor.
   3. Label the transparency with the player, shot number, hand position, and whether the shot was made (1) or not (0).
   4. Use your video camera's frame-by-frame playback mode to "freeze" the ball on the screen so that you can mark the position of the ball on the transparency. Trace the ball's position with a marker.
   5. You will want to advance the video by something like 3–6 frames between each position. Use the same number of frames each time. (Each video frame represents 1/30 of a second. If you mark the ball's position at 10–12 points on its way to the basket, you'll have a good picture of its trajectory.)
   6. You can use a protractor to measure the launch angle. Fit a line through the first few points, and measure the angle between the floor and the line.
   7. Calculate the average launch angle for each hand position for each player and graph the results. Is there a clear relationship between between launch angle and hand position?

Variations

• There are other aspects of hand position that are important for good shooting technique. A basketball coach will have you work on shooting with one hand (the other hand supports the ball, but the shooting hand launches the ball). Design an experiment to compare shooting percentage for one-handed vs. two-handed shooting. Which works better and why?
• You could focus your study on the trajectory of the ball. Is a higher trajectory really more successful as Jay and Jonathan hypothesized? Design an experiment to see whether a high, medium, or low arc results in a better shooting percentage.
• What are the effects of backspin on shooting percentage? Have players shoot from the same position both with and without backspin. Calculate shooting percentage for each method and compare. Does video analysis show any difference in average trajectory for the two cases? Does the ball bounce differently for the two cases? Does this have any effect on shooting success? (TPT, 2006)
• What's the scientific difference between a "soft" shot, and a "brick?" Is it the speed of the ball, the spin, or the arc? Design an investigation to figure out the difference! (TPT, 2006)
• More advanced students can do a quantitative analysis of the video data. Make sure that you have an accurate distance reference in the frame to use for calibration (built-in if you're shooting from a free-throw line—just measure the distance to the basket). Using the equations for projectile motion, you should be able to reproduce the trajectory of the ball. This will give you the launch angle and initial velocity of the ball. What range of launch angles yields the best shooting percentage?

Sources

The idea for this project came from this DragonflyTV Podcast:

• TPT, 2006. "Basketball by Jay and Jonathan," DragonflyTV, Twin Cities Public Television http://pbskids.org/dragonflytv/show/basketball.html.

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