Newton's second law in the golf swing, how important is this?

[Zeph]

I read the article about the Power Pivot by TMO a while ago and has since wondered just how important part of the swing this is.
The part I'm referring to starts a bit down on that link above, under "Conservation of Momentum and Kinesthetic Energy".

The general idea is how much mass you have behind the club at impact and what it does to the ball speed. Imagine two clubs, one having a standard weight head, the other being four times heavier. Let's ignore the fact that it will be difficult to swing, but just imagine you can swing both identically, with the same clubhead speed. The heavier one will hit the ball the farthest because it's weight helps keep the speed of the clubhead up through the ball, creating more compression.

I did think of this myself before I read this article, but didn't quite understand how. I was thinking that the clubhead speed is not the only factor in terms of distance, but also the mass behind the clubhead which drives the ball out there. Anyone can generate a lot of clubhead speed by whipping the club like a madman, but it may not generate a lot of distance.

So, how can we increase the mass behind the clubhead? I'd say you need to be synchronized in the upper and lower body. The lower body must go ahead of the clubhead, but the upper body stay horisontally in the same place (essentially the head) to keep the position you need to strike the ball well. If the lower body does not move forward and lead the way, you'd lose a lot of the mass. Imagine pulling a cart. It's impossible without being in front of it to use your body mass to pull it forward.

Is this partly why when a pro seems to be swinging slow and very much in control, is still hitting the ball a mile, or am I wrong here?

It would be interesting to test this, but it's a bit difficult without having equipment to track clubhead and ball speed. A simulator of some kind would be preferable. What I would like to see is how you can affect the distance by using the mass of the body to drive through the ball and compare it to shots with the same clubhead speed and see how it affects ball speed and distance. You'd of course have to hit the same spot on the club with the same angle of attack.

What do you think?

[tjy355]

Wow, that makes my brain hurt.

I'm more in the Moe Norman school... "just hit that dumb guy with this dumb guy..."

[shortstop20]

You're on the right track IMO.

Pro's have effortless power.

Most of us have powerless effort.

[Adumb]

All of this sounds good, but the problem is the mass of the club and the mass of the golfer will remain the same no matter what. Theoretically if you could swing a 2 lb club at 100 mph and a 7 lb club at 100 mph, you would be able to get more distance out of the 7 lb club. Momentum = (mass)(velocity) and of course this would be like comparing a semitruck going 60 mph on a highway and a car going 60 mph on a highway, the semitruck has more momentum and is therefore more difficult to stop. I think perhaps it has more to do with force. Centripital(sp?) force is the main part of the golf swing. The proper distribution of force within the arc will give you the best swing with the maximum amount of power and distance.

[TMO]

I agree with TMO. Hold on, I am TMO.

Zeph has the right idea. If you want a simple way to think about it just think about maintaining your acceleration through the ball. Tour players do it better than amateurs. You get the most of your swing speed. I think that is simplified enough but maybe I made it too simple. If so, refer to my site :)

[Zeph]

I hit the range today to see if I could figure it out. I did something different. If that was related to this topic I can't tell for sure, but it certainly felt like I got more use of my body in the swing.

Hit the ball very well and longer than normal. I usually don't get the penetrating shot where I can hear the ball hiss through the air. Today it did.
I also tried taking shorter, kind of punch shots. I was amazed that the ball went just as far as with the full swing, sometimes further. This applied for every club in the bag, from wedge to driver. I'm not sure exactly how far my backswing was, I'll video tape it and watch some other time, but it certainly was shorter. The reason I hit it better is probably because the timing and synchronisation was better. I suspect that on a full backswing, the lower body has spent all it's stored energy long before impact. The arms also tend to speed up too early and deaccelerate through impact. With a longer backswing I focused on using the momentum of the club to drop it from the top and not rushing through with the lower body. The body sort of wait for the arms to drop so the club is in a position from where everything can speed up. I don't want a long backswing, especially with the irons, so I'll do some work on this. Taping or having someone watch me while doing these shorter swings to see exactly how short they are.

I really got the feeling that the body was playing a bigger part and really punching the ball out there. On a bad swing the arms went too fast or the body spun out too quickly.
I first learned about the importance of accelerating at the right time, what TMO called late acceleration, when he did a swing check for me. At first I didn't grasp the meaning behind it, but today I certainly do. Most swing errors occur on the downswing because of bad sync or some part speeding up too early.

Today I managed to swing slow, but powerful at the same time, using the mass of my body to drive through the ball. Would really have liked a ball and swing speed monitor today. Another thing I noticed was that I could crank up the swing if I wanted a bit more distance. Normally if I try to smash the ball, the result is disaster. When I got this right however, I was able to swing hard and fast through the ball and it launched out low and penetrating with a bit more distance, without losing accuracy.

With speed at the right place, you will ofcourse hit it better, but I could swing slow and nail the shots. I tried a few shots with my old (hopefully) swing where I tried to swing fast. The result was a higher shot and less distance. I'm absolutely positive I was able to hit the ball further and better with a lower swing speed. Because of the better sync and use of my body, the ball speed went up.

[iacas]

So, how can we increase the mass behind the clubhead? I'd say you need to be synchronized in the upper and lower body. The lower body must go ahead of the clubhead, but the upper body stay horisontally in the same place (essentially the head) to keep the position you need to strike the ball well. If the lower body does not move forward and lead the way, you'd lose a lot of the mass.

I think that keeping your body back does nothing to add "mass" at all, and that's a faulty way to think about it.

A steady head keeps the bottom of your swing in the same place, leading to better impact. A good turn leads to good clubhead speed. Besides, mass is only a small part of the kinetic energy equation: 1/2mv^2 - it's far more important to increase clubhead speed than to increase mass.

[Zeph]

Not sure what you mean about keeping the body back. The lower body go ahead, but the head stay in place to keep the position.
I'm no theoretical physicist, so the kinetic part of all this is beyond me.
By using the equation, can we calculate how important mass is compared to speed? I haven't recorded swing speed, which is why I'm still not certain about this. It could of course be that I'm generating more clubhead speed with a better swing where the body is used better to generate the speed.

The ball reacts to swingpath, angle of attack and point of impact at the clubface, with these in place, the swing speed will determine the ball speed and spin. As long as you hit it well, it doesn't matter of course, but it would be interesting to have something to record the swing speed with and see how it changes with different shots.

When shortening the swing and doing the punches, I actually imagined the swing video of your bending 7i Erik.

[iacas]

Not sure what you mean about keeping the body back.

And I wasn't sure why that was part of your discussion about mass. You're the one that mentioned it first. I was simply trying to dismiss it as "has nothing to do with the 'mass' and the corresponding effect on ball speed."

By using the equation, can we calculate how important mass is compared to speed?

Who cares?

What you should have taken from my post and the formula is that velocity is a heck of a lot more important than mass. It's squared, after all. Would you rather be hit by a VW Beetle going 50 MPH or a semi truck filled with bricks going 5 MPH? Will a ball go further being struck by an iron traveling faster or weighing a little more?

It could of course be that I'm generating more clubhead speed with a better swing where the body is used better to generate the speed.

Uhm, yes, or your swing path is better, or you're de-lofting more, or the shaft is unloading a little better... it has nothing to do with the "mass behind the ball."

[uttexas]

The pros do such a good job of maintaining lag (wrist cock) on the forward swing, then just before impact release the clubhead with full extension of their arms (creating a long lever arm)

Thus, at impact, they have great accellerattion through the ball with a long lever arm transfering force through the ball.

They also have fantastic, synchronized weight transfer that delivers the strike efficiently and on the sweet spot.

[zeg]

I think that keeping your body back does nothing to add "mass" at all, and that's a faulty way to think about it.

This is correct. As we've seen in videos, the club shaft is whipping around on the timescales of the collision. That means it's not providing a rigid connection between your mass and the clubhead mass. The only way to add effective mass to the club head is to add it below the wet noodle tying you to the club head.

Besides, mass is only a small part of the kinetic energy equation: 1/2mv^2 - it's far more important to increase clubhead speed than to increase mass.

Your statement about energy is true, and your conclusion that speed is more important than clubhead mass is true, but it's not necessarily a direct connection between the two. The velocity of the ball is limited by momentum conservation rather than available energy. The heavier the club head is relative to the golf ball, the less of its energy it transfers, but the faster the golf ball will launch.

The difference between energy and momentum limiting is important. Pretending that no momentum is transferred through the shaft during the collision, the golf ball will launch at 2 * head velocity * head mass / (head mass + ball mass). This tops out at twice the head velocity. Once your head mass is much heavier than the ball, you completely lose the benefit of adding further mass. At that point, it's all about velocity. If it were limited by available kinetic energy, there'd still be a gain from adding mass... Does anyone know a typical clubhead mass? I'm curious how they compare to the ball mass. In the end, of course, adding mass DOES limit your ability to swing, so it's definitely a theoretical discussion.

[TMO]

I love to see the debate here but I have to throw in something else. I won't say much but isn't the formula that you would use to figure the amount of energy transferred to a golf ball significantly more complicated. In an isolated system, yes, you can rely on energy to be transfered in a very predictable way. However, this isn't just like you are throwing the club head at the golf ball at a 100 mph. Where you add in a larger mass (golfer) that is providing the momentum to the golf club head then don't you have to account for not just impact but seperation as well?

Sorry if I just made this more complicated for those of you that don't speak nerd.

[iacas]

Sorry if I just made this more complicated for those of you that don't speak nerd.

It doesn't matter. The "take away" point is that, given the choice between adding "mass" and adding clubhead speed, you should always choose clubhead speed if you're looking to increase ball speed (within reason - a clubhead made of an aluminum can might be able to be swung rather quickly...).

That, and "mass" in this situation has nothing to do with where your body is.

[zeg]

I love to see the debate here but I have to throw in something else. I won't say much but isn't the formula that you would use to figure the amount of energy transferred to a golf ball significantly more complicated. In an isolated system, yes, you can rely on energy to be transfered in a very predictable way. However, this isn't just like you are throwing the club head at the golf ball at a 100 mph. Where you add in a larger mass (golfer) that is providing the momentum to the golf club head then don't you have to account for not just impact but seperation as well?

You're right, it's not quite the same as throwing the club head, but it's also not like you're throwing the whole golfer. There are two reasons I suspect that the free collision model is reasonable. First, as I mentioned, the shaft is probably not all that rigid on these time scales. Its stiffness will transfer some momentum, but it'll be less efficient than a rigid attachment. Second, the club head is the only mass that's moving with much velocity. It's moving a LOT faster than your hands, so the bulk of the available momentum is in the club head. This is a bit sketchy, but I don't have time or brainpower available to really work it out.

So I think the collision model is probably reasonable as a rough upper bound on ball launch velocity. Other complexities, such as compression, etc, will actually reduce the launch velocity. The simple collision model assumes 100% of the energy and momentum are conserved. In truth some of the energy will go to heating the ball as it compresses and expands, so it will wind up accepting less momentum than it "should." This also doesn't account for spin, which could be important. I was thinking about drivers where the collision is much less glancing, but that will serve to further reduce the launch velocity.

[zeg]

(within reason - a clubhead made of an aluminum can might be able to be swung rather quickly...).

Now you're making it interesting! I think we'll have to model the wind resistance on the club head now. Any fluid dynamicists in the house?

[TMO]

You're right, it's not quite the same as throwing the club head, but it's also not like you're throwing the whole golfer.

Agreed. This explains why a golfer like Charles Howell III can hit the ball farther than Lumpy. It is not the golfer you are throwing but how efficiently the golfer hits the golf ball.

So here is my very, very brief take away (since Erik did one). 1. Swing speed is important (duh!) 2. Impact is important (duh, part 2) 3. Maintaining your swing speed through impact leads to the most amount of energy possible being transfered to the golf ball. 4. Thus, ball go far.

[iacas]

I'm going to answer the question: it's nearly 100% unimportant.

[Zeph]

Ok, I got my answer. Even though it didn't matter as much as I originally thought, I made a change in my swing for the better. Regardless of what the reason is, I've improved because of trying to sort out this topic. I'm happy.

Now I've got a chance to put it to the test at the Nordea Pairs tournament I'm playing on sunday.