Abstract

Objective

Determine how club head velocity affects shot distance.

Introduction

If you watch any golf on television, you have seen Tiger Woods drive a golf ball, often for well over 300 yards. What are the key factors that affect the distance the ball travels after Tiger, or any golfer, hits the ball? Some of the key factors are where the ball strikes the club face (preferably the “sweet spot”); the loft, or face angle, of the club; and the velocity of the club head at impact. Bu it’s actually the momentum of the golf club head that really matters. Momentum takes the mass of the club head into account. The momentum of the club head equals its velocity times its mass:

Equation 1:

P = MV

When the golf club head strikes the golf ball, it transfers some of its momentum to the golf ball. Momentum has a very special quality: it is conserved. That means that the momentum gained by the golf ball must be accounted for in momentum lost by the golf club. In theory, there will be no overall loss of momentum in the process of hitting the ball, but in reality some momentum is lost to friction, the change of shape of the golf ball after it is hit, and other factors. But for the purposes of this science fair project, you will assume that the momentum of the ball equals the momentum change of the club.

Equation 2:

Momentum of golf ball = (Initial momentum of the club head) − (Final momentum of the club head)

The golf ball will go farther if the momentum of the club head is increased, either by increasing its mass or by increasing its velocity. Clearly, you can only increase the mass a certain amount before the club becomes difficult to handle (most modern drivers have a club head mass of around 200 grams). So increasing the golf club head velocity is the most practical way to increase drive distance.

The goal of this sports science project is to measure the actual velocity of the golf head and determine how that velocity affects the distance the ball travels. You will use a specialized radar device to measure golf club head velocity. Luckily, the distance traveled by the ball is easy to measure if you have a driving range nearby! Let’s tee off and get this project started.

Figure 1. A golfer gets ready to drive the golf ball. (Wikipedia, 2005.)

Terms, Concepts, and Questions to Start Background Research

• Loft
• Momentum
• Velocity
• Mass
• Conserve
• Radar

Questions

• Based on your research, what are some other quantities, besides momentum, that are conserved in any process?
• What is the mass of an "average" golf ball?
• What is the definition of momentum?
• Based on your research, what does the elasticity of a golf ball measure?

Bibliography

• Bailey, R. (2002). Physics of the Drive in Golf. Retrieved August 26, 2009, from http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/Randolph_Bailey/Web%20Project/index.htm.
• Fritz, J. (2002). Physics of the Golf Swing. Retrieved August 26, 2009, from http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/josh_fritts/swing.html.

Materials and Equipment

• Golf club. Use a driver if you are comfortable with it. You can also use a fairway wood (5-wood, for example) or a long iron (3-, 4-, or 5-iron).
• Golf balls
• Driving range
• Golf club radar, such as the Sports Sensors Swing Speed Radar; available from Amazon.com at www.amazon.com
• Optional: Binoculars
• Optional: Two experienced golfer helpers
• Lab notebook

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Experimental Procedure

1. Read the instructions that came with the golf club radar.
2. Go to a driving range and set up the golf club radar, as instructed.
3. Hit several golf balls.
1. Use a golf club with which you can consistently hit the ball in a straight line.
4. Practice using the golf club radar so that you can get good readings of your club's head speed.
5. When you’re comfortable with your swing and the equipment, hit golf balls at various club head speeds, as follows.
1. Hit all of the balls in the same direction.
2. Use at a variety of club speeds, from slow to fast. Try to be consistent with each speed of swing.
3. Hit at least three strokes at each speed.
4. Record the distance at which the ball comes to rest.
5. Don't record the distances for balls that are shot far to one side or are otherwise "muffed."
6. Repeat the entire procedure two more times to demonstrate that your results are accurate and repeatable.
7. Graph the data.
1. Convert the distances to meters (m).
2. Convert the club head speed into meters per second (m/s).
3. Average the distances and club head speeds.
4. Graph the average distance the ball traveled on the x-axis and the average club head speed on the y-axis.

Variations

• Try different clubs. Does the loft (face angle) affect the results? Hint: You could graph the loft angle on the y-axis and the distance on the x-axis, keeping the swing speed constant.
• How does club speed relate to the golf ball’s time of flight (i.e., how long the ball is in the air)? Use a stopwatch to measure time of flight.
• Devise a way to measure the velocity of the golf ball right after it is hit. Graph club velocity vs. ball velocity. Use this data to calculate the final velocity of the club head. Hint: See the equations in the websites listed in the Bibliography.
• Have your helpers also hit golf balls and graph the data for these strokes too. Does the distance the ball travels depend only on the club speed, or do different people get different distances even when the club speeds are the same?
• Measure the exact distance the balls traveled using a surveyors wheel. You will need to obtain permission at the driving range or perform the procedure in an open area where you can safely hit the golf balls.

• For more science project ideas in this area of science, see Sports Science Project Ideas.

Credits

David B. Whyte, PhD, Science Buddies

Last edit date: 2010-01-29 12:00:00