Golf Clubs, Loft Angle, and Distance

Objective

The goal of this project is to measure how the initial launch angle of a golf ball affects how far the ball travels.

Introduction

As everyone knows, the goal in golf is to hit the small white ball into the cup on the green, using the smallest number of strokes possible. Golfers can carry up to 14 different clubs, each intended for a specialized purpose. There are drivers to get the maximum distance when teeing off, fairway woods for hitting long distances when the ball is no longer on the tee, irons for various distance ranges, pitching wedges and sand wedges for chipping shorter shots onto the green, and a putter for the final shot(s) on the green.

This project will focus on the irons, the mid-range clubs often used for shots approaching the green. The irons in a typical set of clubs are numbered 3–9. As the number of the iron increases, so does its loft angle—the angle of the club face with respect to the shaft of the club (see Figure 1). A three iron has a loft angle of 15°. The nine iron has a loft angle of 45°. In between, the loft angle increases by 5° with each iron.

diagram showing the loft angle of a golf club

Figure 1. The angle between the club face and the shaft is the loft angle of a golf club. The diagram shows the club head as it would look if you were facing the golfer and your eyes were at the level of the ball.

As the loft angle of the club increases, the ball will be launched at a higher initial angle. The distance that the ball travels will be determined by how fast the club is moving when it hits the ball, the angle of the club face to the ball at impact, and the amount of spin imparted to the ball. Just after impact with the club, the ball will have an initial launch angle, an initial velocity, and an initial spin rate. These parameters will largely determine the flight of the ball (other factors such as wind or collision with an object can also influence the flight).

The goal of this project is to determine the relationship between the loft angle of the club and the initial launch angle of the ball, and between the loft angle of the club and the distance that the ball travels.

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:

Loft angle
Launch angle
Spin
Initial velocity

More advanced students should also study:

Momentum
Elastic collisions
Inelastic collisions
Projectile motion

Questions

The irons in a set of clubs differ slightly in shaft length. What effect do you think these differences would have on:
- speed of the club head at impact with the ball?
- distance that the ball is hit?
Are there differences in mass of the club head between the irons in your set of clubs? If so, what effect would these differences have on:
- speed of the club head at impact with the ball?
- distance that the ball is hit?

Bibliography

For basic information on golf clubs (purposes of the different types, typical distances for clubs), see:
- Pinemeadow Golf Products, Inc., 2007. "Golf Lesson #1: The Basics of Golf Clubs," [accessed April 12, 2007] http://www.pinemeadowgolf.com/clubs101_1.html.
- Kelley, B., 2007. "Golf Club Distances," About: Golf, Golf.About.com [accessed April 12, 2007] http://golf.about.com/od/beginners/l/blclubdistance.htm.
For more information on projectile motion and momentum, see:
- Henderson, T., 2004a. "Vectors and Motion in Two Dimensions," The Physics Classroom, Glenbrook South High School, Glenview, IL [accessed April 12, 2007] http://www.glenbrook.k12.il.us/gbssci/Phys/Class/vectors/vectoc.html.
- Henderson, T., 2004b. "Momentum and Its Conservation," The Physics Classroom, Glenbrook South High School, Glenview, IL [accessed April 12, 2007] http://www.glenbrook.k12.il.us/gbssci/Phys/Class/momentum/momtoc.html.
This project idea is from:
Goodstein, M., 1999. Sports Science Projects: The Physics of Balls in Motion. Berkeley Heights, NJ: Enslow Publishers, pp. 83–85.

Materials and Equipment

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

Three different golf clubs (irons)
Driving range with yard markers
Helper
Notebook
Pencil
For measuring the loft angle of your shots you will need:
- Video camera
- Tripod
- TV or monitor for video playback
- Plastic wrap
- Marker
- Protractor

Experimental Procedure

Do your background research so that you are knowledgeable about the terms, concepts, and questions above.
It's a good idea to call ahead to the driving range and ask for a good time to conduct your experiment (sometime when the range is less busy). You want to make sure you'll have enough room to set up your video camera so that you can measure the initial angle of the shot.
Select three (or more) different irons to test. Measure the loft angle for each iron.
Set up the video camera so that you can record a good view of the ball as it is launched by the club.
1. You want to be able to measure the initial launch angle by playing back the video. The ball travels fast, so you'll need a wide field of view in order to catch the ball.
2. It's a good idea to take a practice swing or two, and then go back and review the video to make sure that you can see the ball as it takes off. That way you'll be confident that your video data will be useful.
3. If you should happen to have access to a high-speed video camera, that would be even better.
For each iron that you are testing, hit at least 20 balls. For each ball you should:
1. Try your best to use a consistent swing. The speed of the club and the angle of the club face with respect to the ball should be the same (as near as possible) for each shot.
2. Record video so that you can measure the launch angle.
3. Measure the distance that the ball travels. Most driving ranges have yard markers that you can use for this measurement.
4. It's also a good idea to note how much the ball deviated from a straight line. This will tell you how squarely you hit the ball.
Here is how to measure the initial launch angle for each shot:
1. Set up the video camera to play back on a TV monitor.
2. Cover the screen with a piece of plastic wrap.
3. Advance the video to the shot you wish to analyze.
4. Use a marker to mark the starting position of the ball on the plastic wrap.
5. Advance the video one frame at a time through the swing until the ball is hit and starts to fly. Mark the new position of the ball.
6. Continue advancing one frame at a time, marking the position of the ball each time, until the ball leaves the frame.
7. The initial positions of the ball should fall on a straight line. Draw this line.
8. Measure the angle that this line makes with the horizontal. This is the launch angle for the shot.
For each club, calculate the average launch angle.
1. How does the launch angle compare the loft angle of the club?
2. More advanced students should also calculate the standard deviation of the launch angle. Did you have a similar "spread" of launch angles for each club?
Make a graph of the distance (y-axis) vs. launch angle (x-axis) for each shot. Make a separate graph for each club.
1. How does the distance vary with the measured launch angle?
2. Which club gives you the greatest distance?
3. More advanced students should also calculate the standard deviation of the distance. Did you have a similar "spread" of distances for each club?

Variations

Another important launch variable is the initial speed of the ball. This is determined by how fast the club is moving when it hits the ball. You need very high speed photography to measure this. You can find this type of equipment at some golf pro shops. Maybe you can think of ways to enhance your experiment using this "Ball Launch Monitor" technology to measure your swing with the various irons in your club set.
If you'd like to explore the aerodynamics of golf balls, you might be interested in the Science Buddies project A Cure for Hooks and Slices? Asymmetric Dimple Patterns and Golf Ball Flight.

Sources

This project idea is from: