The motion of a golf ball can be thought of as a projectile, whose trajectory is parabolic and acted upon by gravity. The initial velocity imparted to the ball by the club head can be broken down into both a horizontal and vertical component. Numerous scientific studies have identified the optimum launch angle as 11-20° to achieve maximum distance (Erlichson, 1983). Though drivers are typically 8-10° in loft, the flexibility of the graphite driver shafts increases the launch angle through a split second whipping action (Zumerchik, 1997). Golf clubs have grooves added to their faces to add some friction to the club head, so that momentum is transferred to the ball and backspin is created to generate lift. The difference between a ball with backspin and one without can add up to 100 yards after 2 or 3 seconds of additional flight time (Zumerchik, 1997).
There are several forces that act upon the aerodynamics of a golf ball in flight. The most recognizable force acting upon a golf ball is gravity, which pulls the ball downward and creates the parabolic trajectory common of projectiles. Another force on a golf ball is lift, the force that opposes gravity. When backspin is transferred to the ball from the grooves on the clubhead, the velocity of air on top of the ball (which is moving in the direction of the backspin) is higher than the velocity of air on the bottom of the ball. To counteract this, the Magnus effect generates lift on the ball and pushes it up.
In addition to gravity and lift, another force acting on a golf ball is drag, or air resistance. As a golf ball is sent flying through the air, the molecules that come into contact with the front of the ball exert a large pressure force on the front of the ball (drag). Drag slows down the forward velocity of the ball. As the air comes into contact with the front of the golf ball, the fluid motion of the air becomes turbulent. Turbulent flow can be thought of as smoke from a smoke stack- chaotic and wispy. As the turbulent air swirls around the golf ball, the dimples capture some of the swirls and keep them close to the surface of the golf ball. This means that the boundary layer of air stays close and hugs the ball longer, which means that there is a smaller pressure difference between the front of the ball and the back (when compared to a ball without dimples). The dimples thus allow the golf ball to travel farther than a smooth ball because the golf ball experiences less drag.
By: Trevor Stoddard, University of Utah
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When a player exerts force on the golf ball, he/she swings an average of 4-5 miles per hour. If the player uses a club with a flexible shaft, the act of swinging adds an additional measure of torque as the head of the club also propels forward to connect with the ball. The head of the club has grooves that increase the friction between the club and the ball, allowing the club to more effectively focus the area of contact.
The optimal angle to hit the ball ranges from about 12 to 20 degrees. Putting a backspin on the ball increases lift and can add significant distance to the drive. The dimples on the golf ball itself help reduce drag from the air stream by reducing turbulent air pressure around and behind the ball, shifting the wake further behind the ball, thus allowing for smoother, less resistant flight. Any combination of these variables contributes to how well the ball overcomes the forces of gravity and air resistance.
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Articles by Trevor Stoddard
Articles by Trevor Stoddard.