Asked and answered:

Again, this seems to be your issue:

Exactly, thanks for confirming my thoughts - I was thinking I was crazy.

I don't understand the confusion. Is it not incredibly obvious that a ball falling straight out of the sky will spin back more than a ball 1 inch off the ground if they have identical spin rates? This is why higher ball flights that naturally have lower spin rates can suck back more than lower ball flights with higher spin rates.

I believe you have some incorrect information in your post. I don't know about higher ball flights having naturally LOWER spin rates and lower ball flights having higher spin rates the trajectory and spin are completely controlled by the the factors involved at impact. Obviously, a wedge has higher launch and HIGHER SPIN than a driver (wedges spin in the 10K+ rpm range and launch in the 40+ degree range while drivers launch in the low 2k spin and 9-13 launch angle for tour players). There is a measurement called "Spin Loft" which has been discussed on here previously -this mixed with friction & speed (amongst many other factors) determines spin. If you're discussing why a ball spins backwards upon landing has to do with so many variables that it really can't be simplified (surface firmness, slope, type of ball, etc). Wedge shots that spin the most are hit differently than a player would hit a full-shot, and because of the spin rate they stop or occasionally back up. This spin is imparted by angle of attack, surface of clubface (and any other factors that could cause or reduce friction - sand, grass, moisture), contact on the face (lower = more spin), and loft.

A ball landing on a flat surface will rebound at the angle it lands -- this is independent of spin. Since the original question was "exactly similar conditions" - based on trajectory alone, that is the answer - it will bounce upwards at the angle it lands. The amount it spins forwards, backwards, or sideways is based primarily on spin and highly influenced by several other factors. So, when discussing "exactly similar conditions" I'm taking that to mean everything is exactly the same - launch, AoA, club, path, impact, etc - if you want to launch a ball higher, those could not be exactly the same.

In regards to spinning a ball back towards the player (the yo-yo string shot), do you think it would be easier to spin a ball back 30 feet with a high trajectory/ low spinning shot, or a low traj/ high spinning shot? Now take the same scenario and choose which turf condition would spin it backwards more - soft, slow green or firm fast green?

Thanks to everyone for their input. It seems like the answer to my question is the higher trajectory will stop sooner/spin back more.

In reply to Doc's quiz above, I would say the low trajectory/high spin shot would spin back more, and the soft slow green would also be more conducive to backspin than the hard fast green would.

Also, although I have the answer to my query, the only thing which would differ under my conditions would be launch angle. Obviously the launch angle must be increased to obtain a higher trajectory. But other than launch angle, every condition you could conjure would be identical.

Stop using "spin" to mean 2 different things.

@1:30 we see that she starts the ball just left of the target line and her clubface is closed to her swing path. Martin's proposed fix @2:30 is to have her go MORE in to out. Then when she has the expected results based on ball flight laws (the ball started left and went even more left than before), he blames her for turning her hands over to cause it to hook.

He sticks with his suggestion until she finally hits one with her clubface a little open to the target line, no thanks to him, and claims victory.

All this while saying that Trackman really helps him test and confirm his swing theories.

I read somewhere that the "new" b.f.l's apply more so to modern equipment, especially the ball.

True / false ?

If not, how did the old timers manage to be successful with consistently curving the ball ?

I'm an old geezer (58) (but don't feel old), who learned most of my golf from books like Nicklaus "Golf my way", "Five Lessons", etc. I managed to get down to a 2 at one point back in the stone age.

I played many "curve balls" using the "old laws", obv before any trackman and even mostly before video. From books, practice and trial & error

I mostly played a straigth-ish / slight fade, lining up sligtly left, clubface slightly open, and it worked back in 70's - 90's.

Heh, my sticks are still ~30 yrs old, so maybe the "old laws" still apply for me.

The physics haven't changed. People's understanding has.

How did people with a wrong understanding of the physics get it done? Pretty simple really. Feel isn't real. They weren't doing what they thought and said they were.

Or maybe they were, and it was the ball ?

http://www.bettergolfcoach.com/newballflightlaws.htm

I want to be clear, the original theory was (probably) correct and this is supported by many years of successful teaching. It is outdated now because of the changes in modern equipment - in particular “hotter” golf balls and clubfaces. The modern golf ball flies much further and straighter than the 3-piece soft balata balls, common in the 1950’s to the 80’s. But technology has changed the game, and has also altered the ball flight laws. There is a lot of complicated physics effecting the collision between the club and ball, but the most important element is easiest to understand and that is the change in the elasticity of the ball.

If you drop a golf ball at arms length onto a hard surface, it will rebound, but to a slightly lower height; this is because some of the energy is absorbed through the elastic properties of the ball. The amount of the rebound is at a constant rate over a large range of speeds and is known as the coefficient of restitution, or COR. So a ball dropped from 10 feet that rebounds to 7 feet has a COR of 0.7 and will rebound to 14 feet if dropped from 20 feet. A perfectly inelastic ball (if one were ever to exist) would have a COR of one, and a ball of putty would have a COR of almost zero, not rebounding at all. You could describe the effect of a lower COR as allowing the ball to stay in contact with the colliding surface for longer; this rule also applies to angled collisions. It is a fact that the COR of golf balls has changed over the last 30 years. There is even a considerable variation between the balls available today. I recently tested two golf balls to try and illustrate this change in elasticity over the years. A modern ball dropped from 60 inches rebounded consistently to 44 inches, giving a COR of 0.73. Whereas a balata ball from 1990 dropped from the same height, only rebounded to 36 inches, giving a COR of 0.60 – a substantial difference!


It is easy then, to visualise a high-speed video of a clubface striking objects where the face is (for example) 10 degrees open to the path. If you were to hit a steel ball it would leave the clubface almost instantly at 10 degrees to the path, but strike a ball of putty and it will remain on the clubface and travel along the path, at zero degrees. We may also observe that the cushioning effect of the sand during a bunker shot, will reduce the COR of the golf ball, allowing it to follow the club path for longer. A ball from the 1950’s may have had a COR of less than 0.5, and probably would have followed the club path for some time, before changing direction quite violently, because of the spin created during the impact.


The modern ball, however, when struck solidly, will compress on the clubface then rebound at slightly less than the angle of the clubface, but it will not follow the path of the club.

Interesting stuff. Have they used modern tech to assess the response of old balls off the club? The conclusion seems to rest very heavily on the notion that an old ball is similar to putty/is considerably softer than a modern ball in its reaction to being hit by a golf club and that seems unlikely. Would think the data would be interesting to see. Not sure there is any motivation to spend the effort to find out though.

Yeh, that's ******ed.

No. This is dumb.

I believe the exact ratio of shot influence between face and path varies based on loft of club. I'll say that I could see where in theory if the starting direction of a driver is based 85% on clubface angle (random number) that maybe a lower COR would make that number be 83% or some slightly smaller number.

It would not change the ball flight laws whatsoever though. Keep in mind the target it irrelevant in this discussion. The ball does not know where the target it, it only knows face angle and relative path at impact. Would a lower COR change the ratio slightly, maybe, but the modern laws would not be rendered incorrect. An old ball wasn't literally sticking to the face and being thrown by path out to the right.

The ratio changes based on loft and speed, but it doesn't change the underlying laws.

It should be easy for someone to get some old balata balls and test this. I bet the percentages turn out to be pretty much the same for old vs new equipment though.

That is a long winded explanation for something that has little to do with the ball flight laws. The underlying physics of the collision between the golf club and ball don't change when you reduce the COR.

People have been teaching this wrong for years and it has become ingrained in their way of thinking. Just because something feels right, does not make it so. Ask most high handicaps with a wicked slice to swing on an inside to out path. If they do this with a clubface that is not way open they have no more slice

Most guys feel like they can do it right, but still keep slicing. Why, because feel is subjective and not based in reality. Watch some high speed video of the swing and see the club still coming over the top even when it feels like it is coming inside to out. The high speed data and numbers don't lie!

This is all very interesting to me. I get that target line has nothing to do with it as far as the pure physics of what is happening to the ball as in where it starts and how it curves, but target line matters completely in trying to teach someone how to hit the shots.

If my club path is perfectly on line with the target line at impact (which is what most golfers are trying to achieve in thier mind), but the clubhead is closed, the ball will start left of target and curve more left. This is because the club path is in to out when compared to where the clubface is pointing.

So using this how would you teach someone to hit a draw if they already hit the ball very straight? Meaning that natually they have a clubface that is square to target and the path is also in line with the target at impact.

Do you have them change their target line to the right and swing down that line with a slightly closed face or do you have them aim as they normally would and open the face slightly and try to swing in to out slightly more than that?

I am thinking the first option makes most sense...

I'm 90% sure it's option 2, although from a "physics machine" standpoint I couldn't explain to you why I think that. I will agree that option 1 sounds the most simplistic/efficient.

Right. The only reason I say option 1 is because they don't have to change their swing to accomplish the desired result. Option 2 requires you to learn to swing a little bit different. But I'm not sure so I'm asking. And if it is option 2 then how do you learn to swing more in to out or opposite if you desire a fade.

I think there is a lot of unconscious stuff going on here. Like, just getting the face closed and keeping all the other variables the same sounds like it might be more challenging than what may happen naturally with changing the variables.

Just a word of caution for the higher handicappers (or even mid) who might try to self diagnose path/face issues by looking at their ball flight: If you don't consistently hit the ball in the middle of the face you can't deduce the face and path from the ball flight due to gear effect.

I had a lesson on Trackman last night and hit a ~10 yard fade and the numbers were showing that the face was quite closed to the path. Always knew about gear effect but never realised how much it can impact ball flight. My instructor used some spray on the club face to see impact positions after and it was clear that I have trouble hitting the ball out of the center of the face.

This info explains why, over the years, the method I used to draw or fade around a tree usually resulted in me hitting the very tree I was trying to miss. GRRRRRR

Cool article from GolfWRX re: mud balls (bubba!)

http://www.golfwrx.com/342840/the-sc...-their-flight/

The ping swing robot found that mud on the right side of the ball resulted in big misses left and vice versa

It probably should have been obvious but pretty crazy drop off in ball speed and carry when the mud is on the back of the ball where you make contact.