# Golf Ball Physics **URL:** \ **Category:** Factual Questions\ **Created:** [August 9, 2015, 12:29pm UTC](https://boards.straightdope.com/t/golf-ball-physics/727381 "2015-08-09T12:29:17Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [August 11, 2015, 3:30pm UTC](https://boards.straightdope.com/t/golf-ball-physics/727381/21 "2015-08-11T15:30:19Z")
> [@markn\_1](#): > > Well of course that test is going to impart more momentum to the ball with the weights added, because you said “Re-adjust any motors to get the club head speed back up to the initial value.” Same speed with more mass = more momentum. Maybe you misunderstand, but that was the question of the OP: constant club head speed, and more mass, but the increased mass is at the other end of the club’s shaft. UncleFred’s test would work to show if the idea in the OP is right. By the way, he’s proposing to add more mass to the mechanism that holds the club, not at the club head end. With all the noise sources (wind speed, varying temperature, small air currents, golf ball differences, etc., I don’t think you could measure a difference. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [August 11, 2015, 3:46pm UTC](https://boards.straightdope.com/t/golf-ball-physics/727381/22 "2015-08-11T15:46:35Z")
Well then what he’s really asking is, will a _stronger_ golfer be able to hit a golf ball farther, and the answer is trivially yes. Adding weights to the _moving_ parts to me isn’t quite the same as assuming a heavier golfer, most of whose mass is in his non-moving parts (to a first approximation). To move more mass at the same velocity, you need to impart more acceleration, that is, more force. –Mark ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [August 11, 2015, 3:58pm UTC](https://boards.straightdope.com/t/golf-ball-physics/727381/23 "2015-08-11T15:58:19Z")
Actually on second thought, I’ll retract that analysis, because of the flexibility of the shaft. If the shaft were rigid my analysis would apply, but since it’s not, the momentum of the golfer’s arms aren’t directly imparted to the ball. –Mark ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [August 11, 2015, 4:00pm UTC](https://boards.straightdope.com/t/golf-ball-physics/727381/24 "2015-08-11T16:00:26Z")
It’s not just the rigidity of the shaft either, it’s the rigidity of the entire golfers body. It’s a very minor effect when hitting a golf ball, but consider if you were trying to hit a bowling ball in the same way. ---
**Author:** ![iceiso](https://avatars.discourse-cdn.com/v4/letter/i/3be4f8/32.png) [@iceiso](https://boards.straightdope.com/u/iceiso)\ **Post date:** [August 11, 2015, 4:30pm UTC](https://boards.straightdope.com/t/golf-ball-physics/727381/25 "2015-08-11T16:30:30Z")
Okay, I think I’ve got this figured out. The reason this question is so unsettling for me is because it’s unclear whether the methodology for understanding the launching of this ball is that of constant force or conservation of momentum: Constant force: The head of the club hits the ball and applies a ~constant force (ie. drives “through” the impact) for a short period of time, in which the velocities are matched. In this scenario, the mass of the club/person are irrelevant. All that matters is the force applied by the club. This is akin to when you were a child sitting on a swing and an adult gives you a push. In your quest to go higher, the weight of the adult is irrelevant; all that matters is the force applied to your back. Conservation of Momentum: Self explanatory: momentum = mass \* velocity, and the system’s (ball + club + man) momentum is conserved for moments immediately prior to and after the impact. This would be represented in a test jig by having a weighted free-swinging club that reaches some predetermined velocity immediately prior to hitting a ball. Partially inelastic collisions are most applicable. The caveat for using the Conservation of Momentum is that it doesn’t account for external forces. A real life golf swing can’t be represented as a free swinging implement with known mass and velocity; the reality is that there is a person that will continue to “follow through” the impact. What muddies the waters even more is that a human is not a fixed momentum generation machine. If he was, and was capable of hitting a ball at 150 mph with a 1 lbs club, he’d be able to hit a ball at 300 mph with a 1/2 lbs club, 600 mph with a 1/4 lbs club, 5 mph with a 30 lbs club, and so on… The reality is that our ability to accelerate against a resistance is represented by a curve, and everybody’s curve is different. So, back to the question: I believe that in real life, that most people can swing most “normal” clubs at _about_ the same speed. Upon hitting the ball, the club will slow down (Conservation of Momentum), and a heavier club will slow down _less than_ a lighter club. However, most golfers will follow through with the swing (applies external forces), which maintains a driving force behind the ball, and partially negates the benefit of the heavier club. In conclusion, the heavier club will drive the ball slightly further. However, the benefit will be not as significant as if solely explained by Conservation of Momentum (which would be insignificant to begin with). ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [August 11, 2015, 5:27pm UTC](https://boards.straightdope.com/t/golf-ball-physics/727381/26 "2015-08-11T17:27:50Z")
> [@iceiso](#): > > The caveat for using the Conservation of Momentum is that it doesn’t account for external forces. A real life golf swing can’t be represented as a free swinging implement with known mass and velocity; the reality is that there is a person that will continue to “follow through” the impact. Yes, it can be accurately modeled as a free-moving club head with known mass and velocity. The “follow through,” or whatever the golfer does after impact, has no bearing. > [@](#): > > However, most golfers will follow through with the swing (applies external forces), which maintains a driving force behind the ball I’m not sure I understand that. I think you’re saying that if the golfer is still putting considerable force on the golf club’s rotation at the moment of impact (still accelerating at that point), then it may hit farther. And I can see that as a tertiary factor, but negligible. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [August 11, 2015, 5:38pm UTC](https://boards.straightdope.com/t/golf-ball-physics/727381/27 "2015-08-11T17:38:50Z")
I think what **iceiso** is claiming is that the club applies force to the ball for a lengthy period of time. [This video](https://www.youtube.com/watch?v=2Y57pw_iWlk) seems to refute that. –Mark ---
**Author:** ![doorhinge](https://avatars.discourse-cdn.com/v4/letter/d/a5b964/32.png) [@doorhinge](https://boards.straightdope.com/u/doorhinge)\ **Post date:** [August 11, 2015, 6:57pm UTC](https://boards.straightdope.com/t/golf-ball-physics/727381/28 "2015-08-11T18:57:52Z")
A swung golf club flexes in two directions. When a golfer starts the golf club forward, the clubhead lags behind the golfers hands until the the golfer turns his hands over near the bottom of the swing. Second, cerntrifugal force created by the off-center head bends the shaft downward, flattening the static lie of the golf club by 1/2 to 2 degrees, depending on the flex rating and length of the shaft. A golfball is only in contact with the clubhead for 5 to 7 ten-thousandths of a second. By the time a golfer “feels” the contact, the golfball is already several feet downrange. All things being equal = A “legal” U.S.G.A. golfball weights 1.62oz. Clubheads can weigh between 5 and 8oz. A golfers maximum swing speed can vary between 50 and 130mph. Due to the flexability of the golf shaft, and assuming that both the heavier and lighter golfers can generate the same clubhead speed, identical golfballs will rebound off of identical clubheads at the same speed. A 75mph clubhead speed is a 75mph clubhead speed. ---
**Author:** ![iceiso](https://avatars.discourse-cdn.com/v4/letter/i/3be4f8/32.png) [@iceiso](https://boards.straightdope.com/u/iceiso)\ **Post date:** [August 11, 2015, 8:46pm UTC](https://boards.straightdope.com/t/golf-ball-physics/727381/29 "2015-08-11T20:46:48Z")
For what it’s worth, the driver’s contact time with the ball does not need to be long to significantly increase the ball’s velocity. Consider the effect of barrel length on bullet velocity. A longer barrel increases the length of time that the bullet is driven by the pressurized gasses. As an example, my Google-fu turned up a chart where increasing the barrel length from 10" to 20" increased bullet velocity from 2,750 fps to 3,200 fps, respectively. That increase of ~15% was gained by less than 3 ten thousandths of a second of extra contact time. ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [August 11, 2015, 9:29pm UTC](https://boards.straightdope.com/t/golf-ball-physics/727381/30 "2015-08-11T21:29:06Z")
> [@iceiso](#): > > For what it’s worth, the driver’s contact time with the ball does not need to be long to significantly increase the ball’s velocity. Consider the effect of barrel length on bullet velocity. Sorry, I don’t see how the gun comparison applies to golf balls. Are you saying that a club head’s contact time with the ball can be shorter or longer, at the same speed? I can see that if the club head is still accelerating at the time of impact, the shaft (which functions effectively as a spring), will have some force on it just before impact, therefore it will flex slightly less during impact, and slightly more momentum will be put on the ball. My gut tells me that the difference is negligible. [Previous page](https://boards.straightdope.com/t/golf-ball-physics/727381.md?page=1)