The Golf Swing

Golf Swing Physics
Here is a wonderful article, guest-authored by Rod White, a physicist with the New Zealand Measurements Standards Laboratory. It starts from basic Newtonian physics (like we learned in the tutorial) and shows how a good golf swing works. With animations, videos, graphs, and [completely optional] equations, the article covers both swing technique and club technology and how they combine for power drives.

Modeling the Golf Swing
Starting with the double-pendulum model discussed by Cochran & Stobbs before 1970, mathematical models and engineering models have given us insight into how the golf swing works. Here is a multi-page survey of important models of the swing, and how each further refinement of the model refined what we know about how to swing a golf club.

Accelerating Through Impact: Mandate or Myth
Every golf instructor I've ever read or heard says you must accelerate through impact. Then they extend this advice to mean that you will hit the ball farther -- more ball speed -- because you are accelerating the clubhead through the ball, than if you were simply coming into the ball at a constant clubhead speed. The first is good instruction. The second is not good physics.

Opening the loop -- instrumented grips
Until now, kinetic analysis of the golf swing has been limited by the lack of a way to deduce mathematically which hand, arm, or shoulder -- right or left -- was producing a given force or torque on the golf club. Recently, there have been studies that placed instrumentation inside the grip of the club, strain gauges or sensors to measure more directly what the hands do to the club. This article evaluates two of those studies, by Choi & Park and Koike respectively.

Nesbit or Kwon or MacKenzie?
My favorite swing modelers are Doctors Young-Hoo Kwon, Sasho MacKenzie, and Steven Nesbit. So it pains me to see a rather fundamental technical issue where they are on opposite sides of the question. Let me detail what the dispute is, and finish with where I stand on it and why.

Required grip pressure
How tightly does a golfer have to grip the club in order to make a swing? It is dominated by the force the golfer needs in order to hang onto the club, but there are other forces that might have something to do with it as well.

Why do tall golfers hit it farther?
It's a fact; they do. But you maybe surprised why they do. It's not "longer arc", "bigger wheel", or "leverage", which is what most golf instructors responded when asked.

Stability of the swing plane
Todd Dugan asked me if the swing plane is most stable with the hands moving in the same plane as the clubhead (and therefore, of course, the shaft). I asked him what he meant by "stable". Here is the outcome of that discussion. And the answer is yes for a full swing and not so much for a putt.

The Double Pendulum Model and the Right Arm
Many instructors and some golfers criticize the double-pendulum model of the golf swing as inadequate. The most frequent complaint is that it fails to reflect the role of the right arm (in the right-handed swing). Interestingly, physicists and engineers seldom offer this criticism, because they know how to incorporate the effect of the right arm. Here's what they know that the instructors don't.

Ben Hogan, Lee Comeaux, and the Right Hand Hit
Ben Hogan advocated hitting with the right hand at impact. Recently, Texas instructor Lee Comeaux has been teaching his students a "right-hand slap", which seems very Hogan-esque. One of his students, who has seen marked improvement in his distance, asked me to investigate the physical basis of the improvement. My brief study concludes that, from a physics viewpoint, hitting with the hands at impact produces no additional clubhead speed -- none. That might not prevent it from being effective instruction, though.

Leecommotion, the Right-Side Swing
A better description of Leecommotion, Lee Comeaux's swing, is a swing driven by the right side. One of his students reported significant distance gains, and wanted me to explain why that should be. It took a while, but I think I have an analytical model that explains it. I also have a critique of the swing itself.