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

[retexan599]

What often seems in play for me is the 2nd law of Thermodynamics -- you know the one that says things go from an orderly state to a disorderly state -- that would describe my frequent experience in going from the practice range to the actual course....

[jamo]

Force= Mass* Acceleration

[right handed phil mickelson]

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.

5. The fastest part of the golf swing should be just after impact.

[TheJuice]

5. The fastest part of the golf swing should be

I would rather have the fastest part of my golf swing be instantaneously before impact... why would you want it to be faster AFTER the ball has already been struck? Sure this is a matter of milliseconds, but it is more logical.

In all honesty, you can't break this down to conserving momentum/kinetic energy. Sure you can make inferences, ie velocity is the most important factor, but you are also forgetting about torque (lever arm and the angle associated with it), wind resistance, friction, and a seemingly endless list of Physics vocabulary words that all factor into the distance/trajectory of the ball.

[iacas]

5. The fastest part of the golf swing should be

Nah, the fastest part of the golf swing should be at impact. Swinging fast after the ball's gone is kind of pointless.

A lot of people cast and telling them to save the speed for after the ball is a great mental image, but the obvious reality is speed is best applied to the ball, not the air.

[chspeed]

Now that we've all proven we have at least a rudimentary understanding of high school level physics, let's move on to basic statistics.

Q1: What percentage of professional golfers on the tour have *ever* thought about any of this?

Q2: What percentage of physics professors are scratch golfers?

Q3: How many handicap points will you improve by understanding the physics of golf?

All answers are close, or at 0. :)

Seriously, though, if you get off on physics (I do), read Homer Kelley's Golfing Machine. Bizzare book, but utterly useless IMHO.

[enduro]

Nah, the fastest part of the golf swing should be at impact. Swinging fast after the ball's gone is kind of pointless.

You're actually wrong on this one. The absolute fastest part of the club really is slightly after impact when the arms are straight. This is the physics of the proper golf swing. And the reason why is because the club doesn't just hit the ball in the smallest fraction of time.

If the absolute fastest moment was when you hit the ball you would actually be decelerating into the ball. To get the compression you desire the club has to be accelerating as it hits the ball and keeps hitting the ball and then after the ball pops off. So, you're still likely accelerating a small amount after you hit the ball and the arms get straight. It's splitting hairs but the truth is the club is at its absolute peak right after you hit the ball.

[BTGolfer]

You're actually wrong on this one. The absolute fastest part of the club really is slightly after impact when the arms are straight. This is the physics of the proper golf swing. And the reason why is because the club doesn't just hit the ball in the smallest fraction of time.

Regarding the 'fastest moment was when you hit ....', this would seem to be mathematically impossible. To decelerate your velocity must decrease and if you are at your maximum speed you can't have decelerated.

And the club can hardly be at its peak speed right after you hit the ball. The clubhead gives up some very serious momentum to the ball at impact (IOW it loses some serious velocity). What you said just cannot be a correct statement, so I wonder if you intended to say something else. BT

[iacas]

I'm going to try again.

The absolute fastest part of the club really is slightly after impact when the arms are straight.

Not necessarily. The clubhead slows down through impact because the golf ball gets in the way. The best time to be swinging fastest is right at impact. Impact doesn't last long enough for you to be decelerating, and any additional speed after impact is wasted speed - the ball's gone.

A LOT of bad amateurs hit maximum speed before the ball. They decelerate into it, and obviously that's not bad - not because of the "decelerating" part but because they've wasted their speed. A LOT of very good amateurs and some pros hit maximum swing speed a foot or two after the ball. This is also dumb and a waste - the ball's gone. It may be a good mental image for people who cast or something, but it doesn't change the fact that the faster speed should be earlier. If by splitting hairs you are down to the inch or so, then fine. If your fastest speed is an inch after the ball's gone and the shaft kicks back forward and whatever, that's fine too. But if it's even six inches after the ball, you've not swung properly. There's more to generating clubhead speed than straightening your arms. Simple fact: the difference in two drives - one hit with a slightly accelerating 110 MPH clubhead and one hit with a slightly accelerating 110 MPH clubhead (the instant prior to impact) is about two inches of carry. Maybe that ends up with three inches difference total if you include roll. Those numbers come from some experience I have in talking with driver and metal woods engineers. I imagine it's similar for irons.

If the absolute fastest moment was when you hit the ball you would actually be decelerating into the ball. To get the compression you desire the club has to be accelerating as it hits the ball and keeps hitting the ball and then after the ball pops off.

The ball's moving 0 MPH as it sits on the tee. Suffice to say a driver that goes from 110 MPH to 109.88 MPH within the half a millisecond it's on the clubface will compress the ball almost equally as one that goes from 110 MPH to 110.04 MPH (which is a freakish situation, since again the ball slows the clubhead down quite a bit on its own). As far as my memory serves they're reasonably close based on the numbers I saw in 2007. They're not exact, but from my notes they're close.

So far as I know, those are the physics of it. Maximum speed "at" the ball or "at" impact (where "at" is a spot about an inch on either side of the ball, as very few people can even control it that precisely). That's not to say, again, "past the ball" isn't a great swing thought or mental picture or whatever to help people not release their energy/speed prematurely. Edit: Plus, what BT said.

[enduro]

Regarding the 'fastest moment was when you hit ....', this would seem to be mathematically impossible. To decelerate your velocity must decrease and if you are at your maximum speed you can't have decelerated.

From everything I've read it is absolutly true.

Your body is constantly pumping out new energy so whatever you've put into the ball is replaced I believe. I believe the drive of the body is so many times more powerful than the resistance of the ball that balls mass and energy absorption is a non-factor. Like a small asteroid hitting a planet and having no real effect on its movement. And that the body is constantly generating more energy with every bit of turn that you can in fact be at a slightly greater velocity right after impact. But it makes sense. Both arms are not fully extended at impact. The muscles aren't being 100% used. They are slightly after impact however. Also, just the basic physics of circular motion. When both arms are extended... These are such unimportant details and like I said it is splitting hairs. But form Ben Hogan's book to some science paper on the swing I read, I was informed that the club head is at its quickest just after impact. I'm not gonna argue with Hogan!

[iacas]

I believe the drive of the body is so many times more powerful than the resistance of the ball that balls mass and energy absorption is a non-factor.

It's not. Not in the range you're talking about (during impact/compression). In that time frame it's a significant factor. Heck, watch any of those BizHub SwingVision videos and you'll see how much the club can deflect at impact. It's significant.

And again, if you're somehow faster a foot after the ball than the millimeter before it, you've not hit the ball as far as you can. You can't decelerate enough in that millimeter to slow down to the speed you must have achieved in the swing where your max speed is a foot or two after impact.

Both arms are not fully extended at impact.

There's a lot more to power than extended arms. The hips stop going forward at impact, too. Tiger's right arm doesn't fully extend until his clubhead is two feet past impact, and I guarantee the clubhead isn't moving faster then than it was at impact.

Also, just the basic physics of circular motion. When both arms are extended...

Actually, the length of a line from the left shoulder to the clubhead at impact is longer than the line from the center point between your two arms (the top of your sternum) to the clubhead. The left shoulder is farther from the ball at impact than your sternum - thus a longer radius.

[iacas]

Oh, and go to 6:00 into this video: http://video.google.com/videoplay?do...69365872074822 . I'm reviewing Sonic Golf (probably in a week the review will be up), and that's what prompted me to dig out my notes from 2007 and the time I spent with engineers. I've talked about it a few times with various swing instructors, too.

Again, I'm not interested in splitting hairs say an inch or two on either side of impact. Almost nobody (I'm saying almost in case Tiger Woods is included here) can control it much better than to within +/- 1 inch. But I am talking about "max speed" being a foot or so past impact - that would be bad.

[enduro]

Actually, the length of a line from the left shoulder to the clubhead at impact is longer than the line from the center point between your two arms (the top of your sternum) to the clubhead. The left shoulder is farther from the ball at impact than your sternum - thus a longer radius.

Well, Ben Hogan is wrong then.

I wouldn't recommend being at your peak velocity a foot after though. In your example, imagine if the maximum velocity was a millimeter after impact. You would have a better shot than if it was a millimeter before impact. We are dorks.

Again, I'm not interested in splitting hairs say an inch or two on either side of impact. Almost nobody (I'm saying almost in case Tiger Woods is included here) can control it much better than to within +/- 1 inch. But I am talking about "max speed" being a foot or so past impact - that would be bad.

Oh yeah, please don't confuse me. I'm talking right after impact, not a foot or something, lol. Like an inch or something!

[iacas]

Well, Ben Hogan is wrong then.

No, because what you feel is often quite different from reality.

I wouldn't recommend being at your peak velocity a foot after though.

OK. Because until now you haven't made that clear. Both of your arms don't straighten until about a foot or two after impact, and you keep listing the arms as relevant.

In your example, imagine if the maximum velocity was a millimeter after impact. You would have a better shot than if it was a millimeter before impact.

Yes, by about an inch or two. And again, given the ball, that's incredibly hard to do. Took a robot to do it in the testing - the engineers said no human could do it - to overcome the loss of speed caused by the ball that quickly after impact (and we were talking about that inch I've mentioned).

Anyway, I'll put the discussion to rest if you are. And quite likely even if you aren't.

[lobsterzilla]

im with erik on this one

[iacas]

im with erik on this one

Thanks. But to sum things up, I think the take-away value of that discussion is this:

The advice that the fastest part of your swing should be "after impact" is great for people who cast or expend energy too soon, but in reality you want to be at your fastest "right near impact" (within an inch or two). If you hit maximum speed at any other point, your golf swing is not as efficient as it could be.

[enduro]

Thanks. But to sum things up, I think the take-away value of that discussion is this:

Right, it's a to-ma-toe, to-ma-ta thing here. We're both saying the club should be at maximum velocity right around where the ball is struck.

I don't see anymore need for discussion here. Really this thread should have died when it was pointed out that since velocity is squared, it is far more important to Force than mass.

[RC]

Erik has said it about as well as a short discussion could have it. There is speed and there is acceleration to think about. Obviously, the shaft is unloading, so there is no way the same acceleration is happening just prior to impact. The acceleration is actually decreasing earlier in the downswing than you might think, while the velocity is still going up -- just not as rapidly as before. Check a shaft two or three feet before impact. It is strongly flexed and starts unloading because you are not accelerating the club as much as before. If you can keep accelerating all the way to impact, you will still be accelerating less than you were earlier in the swing, the rate of increase in speed is bleeding off rapidly, but you are trying to maintain a little more speed if possible. My guess is 90 percent of golfers are not even maintaining their maximum speed all the way to impact (hey, just a guess here.)

The speed the club is moving needs to be maintained at impact... that is the hardest thing to do. So it should feel like you are accelerating and gaining speed through the ball, but you really are not increasing speed or if so, just barely. The whole secret of a high speed, good swing is to not doing anything that causes the club to slow down. mv=mv for the club, golfer and ball. So unless the golfer is producing a lot of new acceleration, the club is very unlikely to be speeding up after impact.