The tiny dimples present in golf balls are necessary to increase the drag a little. These dimples also increase the so-called Magnus lift which is unique for lifting as in the case of a rotating bodies going thru a medium. Since the golf ball has backspin, Magnus lift is required. The Magnus lift can force a ball to hook or slice if it is equipped with sideways spin.
In defiance to layman’s concept regarding trajectories contained in a vacuum, golf balls do not pass in inverted parabolas; they go on the way of an impetus trajectory. The reason for this is that the combination of drag, which lessens the speed horizontally in the trajectory and Magnus lift, which holds the ball during the first part of the trajectory enabling it to go straight.
The trajectory can even tilt on an upward direction initially, depending on the situation. In this case, you will see a golf ball flying high with significant vectors. When the player hits the golf ball, it flies in the speed of 70 m/s and a corresponding backspin of at least 50 rev/s. The Magnus lift is presumed to exist due to the relative drag on the wind on top and below portions of the golf ball.
The top part moves slower in accordance with the air surrounding it, therefore, there is lesser drag on the wind that goes with the ball. The boundary layer is thin and the air in a nearby region moves swiftly following the ball. The bottom portion goes quickly depending on the air’s movement. You can feel that more drag occurs on the air passing thru the bottom and the perimeter layer is thick.
The air in the nearby region goes slower relative to the ball. This is based on Bernoulli force theory that creates the lift. In this process, we can say that the flow lines on the ball are undergoing displacement on downward direction making the ball to be pushed up. Pressure occurs near the transition region of laminar flow and turbulent flow. However, turbulent flow can adjust on a surface easily than laminar flow.
Therefore the result is that the laminar flow lines on the top separates from the surface and a net displacement of the flow lines goes in an upward direction. Here, the Magnus lift registers a negative strength. The dimples of the golf ball helps in the quick formation of a pressured boundary layer along the flight of the golf ball thus allowing more lift.
If there were no dimples in the golf ball, the ball will flight in a parabolic trajectory going down easily and not landing straight downward. It was discovered unintentionally at the early stage of golf where golfers observed that rough golf balls can go farther.
Even if there is drag, a golf ball with dimples can go a better distance in air than it could in vacuum given the same speed and angle. But a golf ball hit at 45 degrees and 70 m/s in the atmosphere can go 500 meters more at the initial bounce.