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  #1  
Old 05-23-2010, 02:13 PM
charlie145 charlie145 is offline
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Golf ball deforming, true or false?

Surely the outer layer of a golf ball is too brittle to deform so much, what's the SD?

Anim gif
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  #2  
Old 05-23-2010, 02:21 PM
Shagnasty Shagnasty is offline
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I don't that is a valid video for a normal gold ball but they do deform some. This video is more believable:

http://www.youtube.com/watch?v=2Y57p...eature=related
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  #3  
Old 05-23-2010, 02:45 PM
mhendo mhendo is offline
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Here's a YouTube video version of the OP's animated GIF. According to the person who posted it, it's traveling at 150mph, and hitting a steel plate.

FWIW.
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Old 05-23-2010, 02:52 PM
postcards postcards is offline
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The OP's golf ball shows up as the second video in Shagnasty's link, claiming to be a 70,000 fps of a golf ball at 150mph.

Would 150mph be enough to flatten a ball?
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  #5  
Old 05-23-2010, 03:12 PM
Fear Itself Fear Itself is offline
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Quote:
Originally Posted by charlie145 View Post
Surely the outer layer of a golf ball is too brittle to deform so much, what's the SD?
What makes you think a golf ball cover is brittle?
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  #6  
Old 05-23-2010, 04:24 PM
LSLGuy LSLGuy is offline
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If you cut a golf ball apart, you'll find that the outer covering is flexible plastic. You can easily squash a hemisphere of the outer covering flat like a taco just between your fingers.

Now a complete golf ball is another story. Those don't squish much even using Channel Lock plies. But that's because the interior is full, not because the cover is brittle or stiff. If you have a decent-sized bench vise, you can squash a golf ball with it to maybe 60-70% of the ball's normal diameter.

A golf ball is a very stiff spring. But it is a spring, and the reason it leaves the club head so quickly is precisely because it does deform so well under the range of impact forces typical golfers can create with their clubs.

Somebody who could get the club speed up to 10x what Tiger Woods can would probably find most balls bursting on impact like an egg. Meanwhile, when a kid putts one at mini golf, it deforms almost zero.

Last edited by LSLGuy; 05-23-2010 at 04:26 PM..
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  #7  
Old 05-23-2010, 09:01 PM
Chief Pedant Chief Pedant is offline
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Quote:
Originally Posted by postcards View Post
The OP's golf ball shows up as the second video in Shagnasty's link, claiming to be a 70,000 fps of a golf ball at 150mph.

Would 150mph be enough to flatten a ball?
A clubhead speed of 140 MPH deforms a ball, but not nearly to the extent shown.

Here's what it looks like for a typical drive: http://www.youtube.com/watch?v=Aa0j44ydQpQ

Professional long-drive contest winners can reach a clubhead speed of 140 MPH.

http://beauproductions.com/golfswingsws/hititlonger/

I do not know how the video was made, but that is not a golf ball.

It's not unusual for golf balls to break apart, and the typical modern 3 or 4-piece ball would rupture long before deforming so uniformly.

Last edited by Chief Pedant; 05-23-2010 at 09:05 PM..
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  #8  
Old 05-24-2010, 01:41 AM
Mangetout Mangetout is offline
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Quote:
Originally Posted by Chief Pedant View Post
A clubhead speed of 140 MPH deforms a ball, but not nearly to the extent shown.

Here's what it looks like for a typical drive: http://www.youtube.com/watch?v=Aa0j44ydQpQ

Professional long-drive contest winners can reach a clubhead speed of 140 MPH.

http://beauproductions.com/golfswingsws/hititlonger/

I do not know how the video was made, but that is not a golf ball.

It's not unusual for golf balls to break apart, and the typical modern 3 or 4-piece ball would rupture long before deforming so uniformly.
What speed is the clubhead going in the video you linked? (I assume you don't necessarily intend to present it as an example of the 140 MPH statistic you mention)

Also, can we get a cite on the 140MPH clubhead speed? (I don't say it's impossible, I'd just like to hear it from someone not extolling the virtues of his own technique...)
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  #9  
Old 05-24-2010, 06:17 AM
Chief Pedant Chief Pedant is offline
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Quote:
Originally Posted by Mangetout View Post
What speed is the clubhead going in the video you linked? (I assume you don't necessarily intend to present it as an example of the 140 MPH statistic you mention)

Also, can we get a cite on the 140MPH clubhead speed? (I don't say it's impossible, I'd just like to hear it from someone not extolling the virtues of his own technique...)
I'd guess that particular video shows a clubhead speed in the 125MPH range.

I play golf, and watch a fair amount. Among the more common snippets added to otherwise boring shows are closeups of professionals contacting the ball; more recently, high-speed cameras such as Swing Vision create closeups of the ball being struck.

Professional golfers have a clubhead speed for drives in the 120-130 MPH range. They do not swing at absolute full effort most of the time, in order to maintain better control. Long-driver specialists are closer to 150 MPH. See, for instance, this cite from Wikipedia: "Fast swingers can swing their club heads at over 150 mph (245 km/h), well beyond the 85 mph (140 km/h) average for an amateur. They train for strength, flexibility, and speed and often perform corporate exhibitions for money, exhibiting a variety of trick shots."

High clubhead speeds are achieved with a combination of longer-shafted clubs and physical expertise.

Last edited by Chief Pedant; 05-24-2010 at 06:19 AM..
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  #10  
Old 05-24-2010, 06:26 AM
Airman Doors, USAF Airman Doors, USAF is offline
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I'm thinking that the video might be real. It's not really a valid comparison between a steel plate (essentially a wall) and a clubhead because the clubhead has only momentary contact with the ball before the energy is transferred and the ball flies away whereas the contact with the plate is much more solid and the moment of impact is necessarily longer. Think of it as a car hitting a building head-on compared to a car at a stop getting rear-ended.

I suppose it could happen. There's nothing in a golf ball that is so inelastic that it couldn't deform that dramatically.
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  #11  
Old 05-24-2010, 07:00 AM
LSLGuy LSLGuy is offline
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The ball-against-wall video shows deformation vastly beyond that of any ball-against-club video. So it's either not a real golf ball, or it's going a heck of a lot faster than the stated 150 mph, or it's a totally faked vid. My vote is for much higher speed.
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Old 05-24-2010, 10:01 AM
Mangetout Mangetout is offline
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Quote:
Originally Posted by Chief Pedant View Post
I'd guess that particular video shows a clubhead speed in the 125MPH range.

I play golf, and watch a fair amount. Among the more common snippets added to otherwise boring shows are closeups of professionals contacting the ball; more recently, high-speed cameras such as Swing Vision create closeups of the ball being struck.

Professional golfers have a clubhead speed for drives in the 120-130 MPH range. They do not swing at absolute full effort most of the time, in order to maintain better control. Long-driver specialists are closer to 150 MPH. See, for instance, this cite from Wikipedia: "Fast swingers can swing their club heads at over 150 mph (245 km/h), well beyond the 85 mph (140 km/h) average for an amateur. They train for strength, flexibility, and speed and often perform corporate exhibitions for money, exhibiting a variety of trick shots."

High clubhead speeds are achieved with a combination of longer-shafted clubs and physical expertise.
Thanks for that - I'm still not entirely sure that those individual facts are joined up to conclusively point to the video being fake in some way. Is there a slow motion video somewhere with a clubhead verified to be moving at 150mph?

That said, I suspect LSLGuy is on target - the linked video is clearly the result of a fairly expensive and high tech setup - I don't believe it's likely that anyone would go to that much trouble and film footage of a fake ball - more likely one of the other facts has been lost along the way (such as the impact speed.
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  #13  
Old 05-24-2010, 10:13 AM
billfish678 billfish678 is offline
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Quote:
Originally Posted by Airman Doors, USAF View Post
I'm thinking that the video might be real. It's not really a valid comparison between a steel plate (essentially a wall) and a clubhead because the clubhead has only momentary contact with the ball before the energy is transferred and the ball flies away whereas the contact with the plate is much more solid and the moment of impact is necessarily longer. Think of it as a car hitting a building head-on compared to a car at a stop getting rear-ended.

.
IMO thats the explaination.

I gotta admit (regardless of the actual speed) I was pretty amazed a golf ball could deform THAT much. And the rebound dynamics as it changed shape several times were pretty interesting as well. Neat video!
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  #14  
Old 05-24-2010, 01:41 PM
Ravenman Ravenman is offline
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I took the video to mean that the ball was traveling at 150 mph, which would mean a clubhead speed of about 105 mph. That's the swing speed of a pretty good amateur, not a long drive champion. One of those long hitting guys would have ball speeds up around 200 mph.
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  #15  
Old 05-24-2010, 01:56 PM
CalMeacham CalMeacham is offline
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Harold E. "Doc" Edgerton of MIT took tons of photos of golf balls deforming. One of them is up in "Strobe Alley" on thefourth floor of MIT's Building 10, but I can't find a copy online. Here are some low-velocity photos he took in the 1940s:

http://www.tutelman.com/golf/design/...lubmakeronline


But he had much more extreme photos of impacts -- he had long ago taken pictures of deformed footballs at impact and tennis balls and racquets, as well as a great many other things (and so did others in his labs, and the countless students who took his courses). I don't recall seeing any as deformed as the clip in the OP, but it doesn't surprise me at all. I myself took high speed films of karate strikes on wooden boards and concrete blocks. For short enough periods, as seen at high enough frame rates, damned near everything deforms.
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Old 05-24-2010, 03:11 PM
Chief Pedant Chief Pedant is offline
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Originally Posted by CalMeacham View Post
Harold E. "Doc" Edgerton of MIT took tons of photos of golf balls deforming. One of them is up in "Strobe Alley" on thefourth floor of MIT's Building 10, but I can't find a copy online. Here are some low-velocity photos he took in the 1940s:

http://www.tutelman.com/golf/design/...lubmakeronline


But he had much more extreme photos of impacts -- he had long ago taken pictures of deformed footballs at impact and tennis balls and racquets, as well as a great many other things (and so did others in his labs, and the countless students who took his courses). I don't recall seeing any as deformed as the clip in the OP, but it doesn't surprise me at all. I myself took high speed films of karate strikes on wooden boards and concrete blocks. For short enough periods, as seen at high enough frame rates, damned near everything deforms.
I am certainly not going to pretend any expertise on the physics of elasticity and deformation, but I do not believe the video to be a standard golf ball at room temperature. I don't know what happens if you warm up a modern golf ball...at room temperature or below I think it would rupture before this degree of deformation. The timing of deformation recovery also looks too quick too me for a standard-temperature golf ball. Still, perhaps you are correct.

I'm sure you are aware that modern golf balls have little in common with the golf balls shown in those 40s videos, but whether they would be more or less brittle, I cannot say.
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  #17  
Old 05-24-2010, 03:15 PM
ivan astikov ivan astikov is offline
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Quote:
Originally Posted by CalMeacham View Post
For short enough periods, as seen at high enough frame rates, damned near everything deforms.
Hmmm...what happens to the puncher's knuckles? Or is it the heel of the palm they use?

Last edited by ivan astikov; 05-24-2010 at 03:17 PM..
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  #18  
Old 05-24-2010, 03:19 PM
CalMeacham CalMeacham is offline
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Hmmm...what happens to the puncher's knuckles?
On an individual scale, I can't say, but the fingers of the hand don't remain quite as aligned as they are before it hits. A fist remains more "organized", but an open-hand strikes sort of comes apart before reforming.



You want pictures, have a look at the article in the April 1979 issue of Scientific American on The Physics of Karate. There are stills from a high-speed movie of a strike there.
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  #19  
Old 05-24-2010, 03:39 PM
Mangetout Mangetout is offline
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Here's a video of a face slap which demonstrates some of the features CalMeacham mentions.
http://www.break.com/index/face-slap...ow-motion.html

(NB: I am not trying to equate the human face to a golf ball in any way)
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  #20  
Old 05-24-2010, 03:48 PM
CalMeacham CalMeacham is offline
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While slapping faces is fun (and the video demonstrates the malleability of human features), I should note that an open-palm slap isn't even close to the way a karateka holds his hand for s blow that breaks boards, and very far from the way he holds a fist for striking a cement block.


And, while the earlier Edgerton shots didn't show q completely flattened golf ball (which may simply be because he didn't go up to such high impact speeds -- I don't know), he did show golf balls that looked as if their width was reduced by half, with one half of the ball practically squeezed flat, so that it looked like a hemisphere instead of a ball. The page I linked to didn't have that degree of deformation, but, as I say, it's all I could find online.


Doc's photos of a tennis ball did show it being squashed completely flat against the racquet -- but that's not so much of a stretch to believe.
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  #21  
Old 05-25-2010, 07:36 AM
Chief Pedant Chief Pedant is offline
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See here for an article with some photos showing a golf ball striking a steel plate in the laboratory at a speed of 61 m/s, which the Pedant's feeble math skills calculates to be about 136 MPH.

I remain unconvinced the OP video is a real golf ball at room temperature...

Last edited by Chief Pedant; 05-25-2010 at 07:38 AM..
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