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# Importance of Acceleration Thru Impact

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I have been wrong on here many times so I  am basically just trying to understand.  I thought that the club is traveling it's fastest when both arms are straight.  If impact is made with a slightly bent trail arm and then just after impact both arms straighten then wouldn't the club be accelerating, even if slightly through impact?  Even if the clubhead just before impact was 98 mph and then just after impact it was 100 mph and this was the maximum speed attained, that would still be accelerating.  Or would it be correct to say that the speed created doesn't have to be accelerating through impact, but it must be maintained through impact.

I say this becaue I know that I have fast hips, from my baseball days, and so I FEEL (which probably isn't real ) like I wait until almost impact to apply any of my force to my swing.  This has done wonders for my accuracy and has really helped on my partial shot which I had be previously struggling with. I would have thought that there is no possible way that my clubhead could be at max speed because I had not added any assistance to increase the speed yet.  After adopting this method my distances were unchanged if not slightly longer.

I'm just trying to understand.  The "swing easier" tip does absolutely nothing for me.  I my case it is basically find the right point during the swing arch to apply the speed and let the hips fire like they want to.  Interesting thread to say the least.

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What influence on club head speed does impact with the ball have?  One might think the club head speed slows down upon impact. Does the train slow down upon impacting the empty metal garbage can the kids left on the track?  Seems unlikely given the huge moving mass of the train. So too  the club head and ball; the speed and mass of the club head vs the tiny ball= no contest.  Moving the golf ball is not like chopping wood where the impact of the ax does the work and the acceleration of the ax is rapid until it suddenly reaches zero, the log.  Reading the offered graphs i cannot tell if Rory's , or any pro's , club head speed maxs out upon impact or just after. But in my, limited, experience i find it most useful to want to keep the club head going as fast as possible through the ball.  I am ruined if i view the ball as the 'log'.

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Originally Posted by Righty to Lefty

I say this becaue I know that I have fast hips, from my baseball days, and so I FEEL (which probably isn't real ) like I wait until almost impact to apply any of my force to my swing.  This has done wonders for my accuracy [...] After adopting this method my distances were unchanged if not slightly longer.

Wow I'm so glad to see a good player has had this experience.  I too have long had bad hip habits from my baseball days, and the story of the various ways I've tried to fix it would go on for pages.  I've been obsessed enough and know enough now to know what I "should" be doing, but just could never make it feel natural and thus consistent.

I've just recently discovered exactly what you say.  If I feel like I'm barely swinging at all and just float through the sequence and positions I want and feel like I'm not applying any of my force until maybe A6, accuracy vastly improves, everything feels way more in control and athletic, and I don't lose any distance even though I feel like I'm swinging at about 30%.

The magic of leverage and unloading at the right time I guess!

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Originally Posted by mdl

Maybe a charitable interpretation of "acceleration through impact" is that it's a way to encourage not trying to snap from the very top and getting a velocity curve that looks more like Rory's?

As a swing thought it's one thing. It may or may not be a good swing thought for any given individual, or a "feel" for that player.

I was discussing the reality of it, what actually happens.

Originally Posted by Righty to Lefty

I thought that the club is traveling it's fastest when both arms are straight.

Nope. For various reasons, that's not true. The "lever" is up the lead arm, so when the lead arm and the shaft are inline would be a more accurate general description of when the clubhead is moving fastest. Even that's not always true, but it's a better generalization than "both arms straight," particularly since the ball gets in the way and more importantly the TURF gets in the way on most shots struck properly, both of which can dramatically slow the clubhead down.

But no, if both arms straight = fastest clubhead speed, PGA Tour pros would strive to hit the golf ball with both arms straight because they could hit the ball farthest that way. It's not true.

Originally Posted by Righty to Lefty

Or would it be correct to say that the speed created doesn't have to be accelerating through impact, but it must be maintained through impact.

No. Acceleration or deceleration at impact is irrelevant. Impact is so short that the change in speed from impact to post-impact is negligible - in fact, 99.9999% of that change in speed is due to the collision with the golf ball and/or turf.

There are golfers who will achieve max speed AFTER impact (with a driver, almost never off the ground), but these golfers are giving up distance and could be taught to better sequence their motions to produce maximum speed at impact instead of saving energy for after the ball is gone, when it serves no purpose.

Originally Posted by Righty to Lefty

I say this becaue I know that I have fast hips, from my baseball days, and so I FEEL (which probably isn't real ) like I wait until almost impact to apply any of my force to my swing.  This has done wonders for my accuracy and has really helped on my partial shot which I had be previously struggling with. I would have thought that there is no possible way that my clubhead could be at max speed because I had not added any assistance to increase the speed yet.  After adopting this method my distances were unchanged if not slightly longer.

Yes you have. Feel isn't real. Your muscles have fired and you've added speed to the clubhead as soon as you start your downswing.

Originally Posted by joekelly

What influence on club head speed does impact with the ball have?  One might think the club head speed slows down upon impact. Does the train slow down upon impacting the empty metal garbage can the kids left on the track?

Make no mistake about it - the clubhead is essentially a free-floating object at this point and it engages in an inelastic collision with a heavy golf ball (clubhead 200 grams or so, ball 45 grams or so = not like your empty garbage can example one bit).

I could show you the math but I think it's pretty obvious in this video:

Originally Posted by joekelly

So too  the club head and ball; the speed and mass of the club head vs the tiny ball= no contest.

Check your math on that one Joe. The clubhead and ball aren't as far apart in weight as you seem to think.

Originally Posted by joekelly

I am ruined if i view the ball as the 'log'.

Yet another example in the book of "Feel Ain't Real."

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Rory is pretty good at getting maximum speed. He's even said he's worked on this with motion sensors, and working out to get him more in balance, and get his timing better. He was wasting energy before his US-Open win. But if you look at the first picture i posted, the brownish gold line is the clubhead. The 2nd vertical black line is impact. You can see the how much that clubhead fluctuates right after impact. then stabilizes. But look right after impact, its a massive drop off in speed. Your seeing the clubhead loose about half its speed at impact.

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The clubhead accelerating at impact is a sign of an inefficient swing. The clubhead should reach maximum speed at impact. Why would you want your maximum speed AFTER impact? Makes no sense.

Sure it does. It is especially important on those short iron shots, pitches, and green side bunkers to generate backspin. It is also important on drive to compress the ball just a little more and keep it on the club face for that extra micro-second to give it that one last bit of compression to bounce off of. So your maximum club head speed just after impact when the ball leaves the club face. It is just pure science that applies to many applications to accelerate through impact like a boxer throwing a punch, or a tennis racket hitting a ball. Here is a good example by Dave Pelz on bunker shots demonstrating the importance. [VIDEO]http://www.pgatour.com/video/r/instruction/swing_coaches/2010/11/15/inst_pelz_bunker_tip9_10ms1340.pgatour/index.html[/VIDEO]

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Originally Posted by dereckbc

Sure it does. It is especially important on those short iron shots, pitches, and green side bunkers to generate backspin. It is also important on drive to compress the ball just a little more and keep it on the club face for that extra micro-second to give it that one last bit of compression to bounce off of. So your maximum club head speed just after impact when the ball leaves the club face. It is just pure science that applies to many applications to accelerate through impact like a boxer throwing a punch, or a tennis racket hitting a ball.

No, it doesn't. I'm sorry, but feel isn't real and if you're still accelerating after impact, you're wasting energy and your timing and sequencing are off. Your understanding of physics is not in line with reality. Feel isn't real here. A boxer's fist is not speeding up after it's hit the other boxer's face.

Impact lasts almost the same amount of time (to a shockingly small degree) whether you're hitting a lob wedge, putter, 5-iron, or driver. 400 microseconds, give or take a small percentage. You can't "add one last bit of compression."

Let me be clear about this, since it seems to be going unnoticed: FEEL isn't real. You might FEEL like you're still accelerating, and it might work for a lot of people because they're currently decelerating into impact. But you're not accelerating, or at least you shouldn't be, in reality. You may need to feel it, but you're not actually doing it.

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Originally Posted by iacas

No, it doesn't. I'm sorry, but feel isn't real and if you're still accelerating after impact, you're wasting energy and your timing and sequencing are off. Your understanding of physics is not in line with reality. Feel isn't real here. A boxer's fist is not speeding up after it's hit the other boxer's face.

Impact lasts almost the same amount of time (to a shockingly small degree) whether you're hitting a lob wedge, putter, 5-iron, or driver. 400 microseconds, give or take a small percentage. You can't "add one last bit of compression."

Let me be clear about this, since it seems to be going unnoticed: FEEL isn't real. You might FEEL like you're still accelerating, and it might work for a lot of people because they're currently decelerating into impact. But you're not accelerating, or at least you shouldn't be, in reality. You may need to feel it, but you're not actually doing it.

I think he confused the idea of accelerating through impact accelerating INTO impact. They sound the same when you read about them, but are completely different.

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No, it doesn't. I'm sorry, but feel isn't real and if you're still accelerating after impact, you're wasting energy and your timing and sequencing are off. Your understanding of physics is not in line with reality.

I respectively disagree and so do physics and the major majority of instructors. Using the thought you imply is a guaranteed method to promote casting the club and coming over the top. The objective is not hitting the ball. The objective is swinging through to the target. The ball just gets in the way and goes for the ride and gets in the way. The human brain and body is not capable of timing what you suggest. I certainly cannot even begin to teach that. What I can teach, and the brain/body can do is accelerate through the ball. It is very easily to visualize by cracking the WHIP just ahead of the ball, not at the ball as you suggest. The swing does not stop at impact. The biggest mistake beginners, intermediate, and novice golfers make is they accelerate the club at the wrong target or object. Again the object is not the ball, it is the target. If you focus on the ball you will actually be decelerating at impact. There will not be any lag or shaft bend at impact. The club shaft will have already straightened out and starts slowing down causing the club head to catch up or even pass the hands which adds loft and a weak high hit. The secret is to hit through or past the ball to the target. As I stated earlier when you think or try to hit the ball, you accelerate your club at the top of the swing to the ball and will reach its maximum velocity before it makes impact. Accelerating too early will result in either a "cast" from the top, over the top, or an "early release." In either case, the club is actually slowing down by the time it makes impact with the ball. Therefore the big SECRET is constant acceleration is needed to ensure a lagging club head through impact. The only way in the Mind’s Eye is to accelerate or hit through to the target and Crack the Whip at the target past the ball, not at the ball. Here it is in action Notice the bend in the shaft and hands leading the club. There is only 1 physical way to do that: Accelerate through impact.

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The idea you need to accelerate through a bunker shot is crap. Most people think Amateurs don't accelerate through a bunker shot, or give up on it, is false. Most of them over compensate for poor advice and throw off there whole timing. How many Amateurs do you see who chunk a bunker shot, why because they think, "i got to accelerate through the shot", and they release the clubhead way to soon, causing it to bottom out way before the ball.

If you look at a tennis strike's kinetic chain, it has the same characteristics as a golf club. Hip rotation, coupled with torso rotation, up to the arm, then whipped through by the tennis racket, with acceleration of the racket being near zero at impact for MAXIMUM racket speed.

Golf or Tennis, the kinetic chain for the club or racket is a Parabola, meaning that the maximum speed is when acceleration is ZERO. that is basic calculus. For hitting a golf ball or hitting a tennis ball, its speed that counts, not acceleration.

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So am I correct in saying that you can accelerate (good) or decelerate (bad) INTO impact,but it is impossible to accelerate THRU impact because when the clubface makes contact with the ball the net effect is a transfer of energy from the clubhead to the ball and this is what results in the clubs reduced speed  after impact.

That makes sense to me just like the boxer analogy. Even though the intent is to hit through the punch, during the its acceleration it meets resistance, and though the intent is to accelerate, the net effect is a loss of speed upon completion of the punch because of energy being transerred to the victim !

What about on a full rehearsal practice swing where the ball isn't struck?  Since the clubhead didn't meet any resistance does it still slow down abruptly after what would have been impact?

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Originally Posted by mdl

Wow I'm so glad to see a good player has had this experience.  I too have long had bad hip habits from my baseball days, and the story of the various ways I've tried to fix it would go on for pages.  I've been obsessed enough and know enough now to know what I "should" be doing, but just could never make it feel natural and thus consistent.

I've just recently discovered exactly what you say.  If I feel like I'm barely swinging at all and just float through the sequence and positions I want and feel like I'm not applying any of my force until maybe A6, accuracy vastly improves, everything feels way more in control and athletic, and I don't lose any distance even though I feel like I'm swinging at about 30%.

The magic of leverage and unloading at the right time I guess!

I absolutely had to tame this problem and I get the same sensation that you do of really feeling like I'm giving very little effort yet the club rockets off the club face. And since I'm not reacting to a 97 mph fastball it feels like and eternity before I fire my hips but I learned to be patient and wait and my scores  dropped 10 shots within one month of just accepting that was how I was wired. What I feel now shows outwardly when other people watch me swing now also because people now tell me that I have "lazy power" and ask me how is it that I'm not swinging hard but hitting it far !!  Oh yes,,, leverage is a beautiful thing.

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The idea you need to accelerate through a bunker shot is crap. How many Amateurs do you see who chunk a bunker shot, why because they think, "i got to accelerate through the shot", and they release the clubhead way to soon, causing it to bottom out way before the ball.

You just made my point. an early release is casting the club or throwing the club at the ball. Video evidence of good bunker players is over whelming proof because the club club passes the ball out of the trap. See for yourself. Dave Pelz is a Physicist aka Rocket Scientist turned Golf Pro. As for me I am just a retired engineer who enjoys teaching. [VIDEO]http://www.pgatour.com/video/r/instruction/swing_coaches/2010/11/15/inst_pelz_bunker_tip9_10ms1340.pgatour/index.html[/VIDEO] Edit : not sure why the link does not come up as a picture.However it works if you click on it.

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That makes sense to me just like the boxer analogy. Even though the intent is to hit through the punch, during the its acceleration it meets resistance, and though the intent is to accelerate, the net effect is a loss of speed upon completion of the punch because of energy being transferred to the victim

Ever seen George Foreman or Bruce Lee throw a 3-inch knock out jab before? Do you really think they quit at impact, or followed through the punch driving with everything they have at the opponent to the ground?

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I think physics-wise, the difference between accelerating through impact and having no acceleration at impact are negligible for the speed the clubhead will have at impact.  The amount of energy put into the ball from the clubhead's mass and velocity will transfer to the mass and speed of the clubhead after impact, the amount of spin the ball will have, and the mass and velocity of the ball, minus some residual heat from the impact.  Based on some numbers I found on the web and from iacas's masses of the ball and clubhead, a rough calculation based purely on those parameters reduces the velocity, of the clubhead after impact, dramatically.  Now, the percentage of velocity lost if you were "accelerating through impact" versus making sure the velocity was maxed at impact is small.  In REALITY, the velocity at impact will be the highest throughout the whole swing. To make it FEEL better, the notion of saying to try and "accelerate through impact" might help players focus on swinging towards the target, even if they lose a small portion of the possible velocity.

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You just made my point. an early release is casting the club or throwing the club at the ball. Video evidence of good bunker players is over whelming proof because the club club passes the ball out of the trap. See for yourself. Dave Pelz is a Physicist aka Rocket Scientist turned Golf Pro. As for me I am just a retired engineer who enjoys teaching. [VIDEO]http://www.pgatour.com/video/r/instruction/swing_coaches/2010/11/15/inst_pelz_bunker_tip9_10ms1340.pgatour/index.html[/VIDEO] Edit : not sure why the link does not come up as a picture.However it works if you click on it.

I'm pretty sure that's more about loft and glancing blows than acceleration. [quote name="dereckbc" url="/t/63127/importance-of-acceleration-thru-impact/0_30#post_784340"]Here it is in action Notice the bend in the shaft and hands leading the club. There is only 1 physical way to do that: Accelerate through impact.[/quote] That club has already impacted the ball, and possibly the ground (I can't tell for sure becasue the picture is about 5 pixels by 5 pixels). Of course there would be shaft bend.

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The club head passing the ball has nothing to do with acceleration. The clubhead passing the ball has more to do with the fact that you hit the sand first and the sand propels the ball into the air. Its no surprise that you take near full swing in a bunker shot, using sand to get the ball out. Pro's don't flip at the ball, at no point before or at impact is there clubhead ahead of the hands. Meaning at no point have they decreased there speed. The reason the clubhead ends up past the ball, is because the ball is traveling on the sand, which absorbed a ton of the energy, and the club slides through the sand using the bounce. It has nothing to do with acceleration. To say it does it to discount all other factors in a bunker shot that cause the ball to exit the hazard.

Quote:
I think physics-wise, the difference between accelerating through impact and having no acceleration at impact are negligible for the speed the clubhead will have at impact.

Not really, especially for Amateurs who tend to have a big issue with have there weight forward and a flat front wrist at impact. The downswing only last 0.3-0.5 seconds. In that time the clubhead starts at zero and goes up to 85-90 mph. That is a substantial increase in speed in a short amount of time. So even If you mistime your impact by little as a 1/10 of a second, you might loose near 10% of your clubhead speed.

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Originally Posted by saevel25

Not really, especially for Amateurs who tend to have a big issue with have there weight forward and a flat front wrist at impact. The downswing only last 0.3-0.5 seconds. In that time the clubhead starts at zero and goes up to 85-90 mph. That is a substantial increase in speed in a short amount of time. So even If you mistime your impact by little as a 1/10 of a second, you might loose near 10% of your clubhead speed.

OK, i did another calculation for the difference in velocity, between the bottom of the swing with full velocity and an acceleration through impact velocity, with the following assumptions: the down swing starts with shaft parallel with ground, constant acceleration in the swing to max velocity (with other assumptions = about .072miles/s^2), a time of .4s for the downswing (to impact area), a man's arm length of 33", a driver shaft length of 44.5", the speed at the bottom of the swing is 100mph, and that an "acceleration through impact" would mean making the top speed appear at about 35° past the bottom of the swing.  I can do other quantities if you want me too.  To reach that 35° mark from the bottom of the swing takes .026sec making the velocity at that point 106.8mph, an added velocity of 6.8mph.  So, I guess it does make a bit of difference.

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