The Aerodynamic Forces
on a Golf Ball


 

Simple Wing
Aligned with Airflow

Given that golf is the most technical sport, and scientists are the explorers of technology, it was only a matter of time before the two got together. From an aerodynamics standpoint, that didn't happen until near the turn of the century, by which time golf was already hundreds of years old. The science of aerodynamics, however, was still young at that point. It should come as no surprise that the momentous event occurred in Scotland, when physicist Peter Guthrie Tait began publishing a series of scientific papers in 1890, which were pioneering in their recognition that air had a lot to do with a golf ball's amazing trajectory.

No doubt it is counterintuitive that the overall effect of air on the flight of the golf ball is, in fact, very positive. After all, wouldn't wind resistance slow the ball down and make it drop, rocklike, to mother earth? Believe it or not, a shot that flies 230 yards in the normal atmosphere would only fly about 160 yards in a vacuum. How can this be? Strangely enough, golf balls are brethren to wings, and wings don't work if there's no air. By the magic of aerodynamics, the spinning ball makes lift, suspending itself against gravity. So it flies farther even though wind resistance (or drag, as aerodynamicists call it) is slowing down. If the air were to disappear, then the drag would disappear, but so would the lift. The net result? You'd be pulling out the Big Stick for a middling par 3 (assuming you could swing it while wearing a space suit).

Simple Wing at
Angle of Attack
 

Every time we stick a hand out the window at 65 mph (don't try this at home if you live in a 55 state!), we're reminded that air exerts a force on any object moving through it. Scientists like to break this force down into two basic components: drag, which acts directly opposite the motion to slow the object down; and lift, which acts at right angles to the drag and generally upward.

Ball with No Spin

Ball With Backspin

To the uninitiated, watching a golf ball fly is an amazing experience. It hangs in the air for an astonishing length of time, as if supported by a force field. And it flies twice as far as a towering second-deck home run. All of this goodness is possible because of the aerodynamic lift force. But where does it come from?

While a person wouldn't confuse a golf ball with a 747 wing, a wind tunnel might. To the air, they look very much the same. When a simple wing is placed in an air stream and aligned with the flow direction, it simply slices through the air with minimal hoopla, and generates no lift. However, if it is inclined to create an angle of attack, then interesting things start to happen. It deflects the airflow downward, creating an upward reaction force (Newton's Third Law: "To every action there is always opposed an equal reaction" - which we know as the lift.)

A golf ball may look portly next to a streamlined wing, but it manages to do similar things to the airflow. When a golf ball is placed in an air stream, it pushes through the air creating a considerable disturbance (that's the portly part), but generates no lift. Here's the good part: given some backspin, it warps the airflow very much like the angled wing, deflecting it downward and creating lift.