## Tuesday, December 6, 2011

### Force And Golf - Part I

First up, I wanted to direct some readers over to Ralph Perez’s Gotham Golf Blog with reference to a new technology called ‘4D Swing.’ I am a big fan of Ralph’s blog, but I try to keep the topics different because I think that allows readers to get more information for them. I would check out these links on 4dswing:

http://www.gothamgolfblog.com/2011/12/4dswing.html

http://www.gothamgolfblog.com/2011/12/tapio-santala-cto-of-4dswing.html

One more note, for those instructors looking to become D-Plane certified, please be patient as I’ve been very busy with the holidays. I will get everybody up to date in the next week or two.

In this series I will be discussing ‘Force’ in the golf swing. I was discussing this with a friend of mine and we agreed that not only is force crucial in the golf swing, but golfers could benefit from learning about force and then understand how to apply it in their game. But, force actually goes beyond the golf swing, which is what I will discuss in parts II and III.

So, what is force?

Force = Mass x Acceleration

What is mass?

Mass is the amount of matter in an object. This is different from weight because weight is the amount of gravitational pull an object has. Thus, if an object weight 200 pounds on earth, it will have much more gravitational pull than if the object is placed on the Moon. However, it’s mass will still be the same.

What is acceleration?

Acceleration is the increase in the rate of speed. If we are driving a car that is going 60 mph and then we press on the gas to make it go 80 mph, the velocity of the car is 80 mph, but the acceleration is 20 mph.

IMPORTANT TO NOTE: I’m probably not phrasing this technically correct…but, acceleration has more influence on force than mass. That’s why we can’t just make our drivers super heavy in order to increase power off the tee. While the mass increases, the acceleration will likely be less and that dip in acceleration dampens the amount of force we can deliver to the club.

FORCE IN THE GOLF SWING

A big part of this I will get into in part III. But, let’s take a look at a golfer with more of a ‘full sweep release’ versus a golfer with more of a ‘snap release.’

Here’s a ‘full sweep release’ executed by Shane Bertsch.

As you can see, Bertsch ‘releases’ the clubHEAD, downward pretty early. To the layman golfer, they would probably think that Bertsch was bordering on ‘casting’ the club.

Now, let’s take a look at a ‘snap’ release by John Senden.

With Senden’s swing, he waits until the very last second to release the clubHEAD. To the layman golfer, it would appear that he has a lot of lag and is ‘driving the butt of the club past the ball.’

Now, it’s not to say that one is better than the other (in fact, Bertsch’s ballstriking metrics came out better than Senden’s in 2011). But, it’s to say that they are different swings that produce very different amounts of acceleration. In fact, Bertsch generates about 107 mph of clubhead speed compared to Senden’s 116 mph of clubhead speed.

And that difference in clubhead speed is probably, in large part, due to the different style of releases between Bertsch (full sweep) and Senden (snap).

The Golfing Machine discussed this for a bit with its Endless Belt Concept (2-K in TGM). Let’s say you have a rock that is tied to a length of string. Let’s say you want to twirl the rock in a circle from the other end of the piece of string. If you twirl it around in a big circle, like somebody trying to use a lasso, the amount of acceleration will be less, than if you ‘tighten’ the circle. Essentially, Bertsch has a much larger circle than Senden. In TGM, they would say that Bertsch’s ‘pulley’ is larger than Senden’s ‘pulley.’

Let’s say Bertsch wanted to greatly increase his clubhead speed. One way he could achieve this is by developing more of a snap type release like Senden has. That would increase his acceleration and create more force.

The problem is that golf is not based solely upon clubhead speed and power, it also has to do with accuracy and precision. Thus, somebody like Bertsch who attempts to go to more of a snap release, could struggle to do so. Lastly, it’s not that a full sweep release player cannot hit the ball long, but they will require more from their body pivot to help with the acceleration of the club.

Part II – Force and Putting, tomorrow

3JACK

NYC Lagster said...

Thanks for the shout out bud, maybe I'll see you in Orlando.

Cheers and keep up the good work!

Ralph

ericpaul2 said...

Just one comments related to the type of release:

If we assume that the arm-club unit has an effective center of mass, the force required to accelerate that mass rotationally is called torque. The torque required to rotate a mass that is away from the center of rotation is a function of force required to accelerate that mass and the distance from the center.

So, by comparing a sweep release to a snap release, we can see how a sweep release effectively has a center of mass (the clubhead) that is, on average, farther away from the center of rotation and thus requires more torque to accelerate the clubhead.

Taken another way, equivalent torques would produce less acceleration for a sweep release versus a snap release.

Walter said...

I don't understand the physics, so is there someone that can explain why the force=mass x acceleration formula is not appropriate to what determines how far a ball is hit? In one "ideal" physics model, the maximum club head speed is at impact. Maximum club head speeds means that the acceleration is zero at that point! Similarly, at the bottom of a pendulum, the pendulum is at its fastest but its acceleration is zero. Or, stated another way, I'd rather be hit by a car accelerating from 0 to 15 mph than a car slowing down from 100 mph to 85 mph. So is there an expert out there that can explain (or disprove) all of this? Given the club head speed at impact, does knowing the acceleration matter?

P "N" K said...

The confusion is coming from the difference in force - which is Ma (M*dv/dt) and kinetic energy delivered to the ball at impact, where kinetic energy is 1/2*M*v^2.

By KE, it's clear that if you increase velocity by the same amount as mass, velocity gives you a exponential return on investment (^2).

So yes, you'd definitely rather be hit by the 15 mph car that's accelerating than the 85 mph car that's deceling -- mph is the velocity, which in terms of the energy you feel gets squared compared to the mass.