Physics

[iacas]

6 hours ago, GreenhornGolfer said:

This also of course means that a with longer club the head will be going faster and that will send the ball further, the driver will hit the ball further than the 9 iron because its a longer club, and its supposed to as the driver is for hitting the ball the furthest.

You can make a 9I as long as a driver and the driver is still going to hit the ball a lot farther.

The stuff about the clubhead rotating faster than the grip is very basic. Grade school physics.

6 hours ago, GreenhornGolfer said:

So anyway, I've been thinking about how some of these physics concepts apply to other sports since physics can sometimes play different roles in different sports although physics is still physics no matter what sport you apply it to, but I've been thinking specifically about pitching in Baseball, such as when you throw a fastball. When you pitch a fastball, unlike in golf, you're not using a club you're just using your hand so it stands to reason that unlike in golf, you want your hand to be moving at maximum speed at the instant you release the ball. You're not dealing with a club so the physics and the concepts are a bit different. So if anybody here knows much about Baseball and specifically about pitching perhaps I can get some feedback. As for me I just know the basics. It's interesting to see how physics applies to golf and then how it applies to other sports. 

Well, this is a golf forum, so… let's stick to golf.

---

@GreenhornGolfer, we have a lot of other threads and topics here.

There's some physics in that one, for example. Have a look.

[GreenhornGolfer]

13 hours ago, iacas said:

Well, this is a golf forum, so… let's stick to golf.

If this isn't the proper folder to discuss other sports, there is the general sports folder. Perhaps such stuff can be discussed there. 

[saevel25]

Yea, I get what you are saying, but it is still a golf forum. Also, your OP did mention physics and golf, which will pique the interest of a few here. 

Physics in other sports, not so much. 

Also, you can google a lot of physics related to other sports. 

[GolfLug]

I'm catching up now that had a bit more time to read some of the posts. Some good stuff but I do have a grievance about usage of the term 'torque' in this discussion. Can we please stop saying things like "hands apply torque to the club"? Torque is specifically a set of opposing forces applied symmetrically and peripherally about the axis of symmetry (COM) of an article, in order to rotate the core component that contains axis of symmetry. There is no point in a golf swing where this happens in relation to a golf club moving through space. It only moves in a 'circle' because one end of the entire club/hand/arm system is tethered to the body while the other side is not. There is NOT a 'rotational' route etched in the brain that makes it follow a circular route or makes one end go faster than the other. If someone is making top hand go 'backwards' or slowing it down actively and bottom hand forward from A6 to A7, then it is a poor attempt at flipping at best. It's not 'torque'. It's certainly not around its COM and is an asymmetric application at that.

Only legit torque application via hands is twisting the shaft longitudinally about itself at any point. Unless your name is Bubba Watson, if you are deliberately twisting the club face shut or open at any point, then chances are you've already lost the plot and are in damage control mode. 

Please leave 'torque' alone.

Edited August 1 by GolfLug

[iacas]

Vishal, torque does not have to be applied symmetrically or in opposition.

I can apply a force to one side of a center of mass and create a torque.

[GolfLug]

4 minutes ago, iacas said:

Vishal, torque does not have to be applied symmetrically or in opposition.

I can apply a force to one side of a center of mass and create a torque.

Yes you can, but only in case of a constrained COM, which a globally moving golf club does not have. If you consider two ends of the club a in a global cartesian co-ordinate system then yes they will have rotated during the entire swing about it's internal COM but that's because they move loosely in the same direction generally, albeit at different rates. We are not making them move about the COM deliberately in opposite directions, i.e. 'applying torque'. If we did, then yes, that would constitute application of force to create torque about it's COM. But not the case from my perspective. At best the constraint here is at the what, saying very loosely.. the humerus? Way outside of the club.

To me the global swing model is closer to a combo of centrifugal and centripetal forces, with the humerus loosely at the center of the swing, the clubhead at the periphery of the circle and the grip somewhere halfway between the clubhead and humerus. The GRFs job is to keep the center of the circle in the position throughout the swing to counter the dynamic forces in the DS. Obviously our anatomy and biomechanics won't allow perfect centeredness of the swing center but you know what I mean.  

[iacas]

5 minutes ago, GolfLug said:

Yes you can, but only in case of a constrained COM, which a globally moving golf club does not have.

I think you're getting into the coupling point or the couple of the hands, but that's a different ball of wax.

[Ty_Webb]

2 hours ago, GolfLug said:

I'm catching up now that had a bit more time to read some of the posts. Some good stuff but I do have a grievance about usage of the term 'torque' in this discussion. Can we please stop saying things like "hands apply torque to the club"? Torque is specifically a set of opposing forces applied symmetrically and peripherally about the axis of symmetry (COM) of an article, in order to rotate the core component that contains axis of symmetry. There is no point in a golf swing where this happens in relation to a golf club moving through space. It only moves in a 'circle' because one end of the entire club/hand/arm system is tethered to the body while the other side is not. There is NOT a 'rotational' route etched in the brain that makes it follow a circular route or makes one end go faster than the other. If someone is making top hand go 'backwards' or slowing it down actively and bottom hand forward from A6 to A7, then it is a poor attempt at flipping at best. It's not 'torque'. It's certainly not around its COM and is an asymmetric application at that.

Only legit torque application via hands is twisting the shaft longitudinally about itself at any point. Unless your name is Bubba Watson, if you are deliberately twisting the club face shut or open at any point, then chances are you've already lost the plot and are in damage control mode. 

Please leave 'torque' alone.

Any time you apply a force to an object that is not directly through the COM, you're applying a torque. Take a car for example. If a car is moving and you hit the brakes, the only contact point is on the ground. The brakes make the tires slow down which applies a force backwards at ground level. Since that force is not applied directly to the COM, it also applies a torque, which makes the car rotate forwards. The suspension at the front applies another torque upwards to fight against that twist (because the ground is in the way). You can feel the front end of the car dip when you brake. Then, when you stop braking and that force is no longer applied, the tires stop applying that torque to the car and the car feels like it rocks backwards as the suspension evens itself out. That's all torques being applied.

Ignoring the twist forces applied to the club leaves you way short of being able to describe the motion. Otherwise the orientation of the club would never change.

[iacas]

9 minutes ago, Ty_Webb said:

Any time you apply a force to an object that is not directly through the COM, you're applying a torque. Take a car for example. If a car is moving and you hit the brakes, the only contact point is on the ground. The brakes make the tires slow down which applies a force backwards at ground level. Since that force is not applied directly to the COM, it also applies a torque, which makes the car rotate forwards. The suspension at the front applies another torque upwards to fight against that twist (because the ground is in the way). You can feel the front end of the car dip when you brake. Then, when you stop braking and that force is no longer applied, the tires stop applying that torque to the car and the car feels like it rocks backwards as the suspension evens itself out. That's all torques being applied.

Ignoring the twist forces applied to the club leaves you way short of being able to describe the motion. Otherwise the orientation of the club would never change.

Yeah.

I'm not sure what Vishal is really talking about with the "constrained" COM. The club's COM doesn't really change much. Less than the body's does…

We definitely apply force to the golf club to move it both translationally (linear force) and rotationally (torque) to the golf club.

That's what Manzella's alpha/beta/gamma is all about. Even before they switched the reference frame from the global to the club-based one. 😉 

[GolfLug]

1 hour ago, Ty_Webb said:

Any time you apply a force to an object that is not directly through the COM, you're applying a torque. Take a car for example. If a car is moving and you hit the brakes, the only contact point is on the ground. The brakes make the tires slow down which applies a force backwards at ground level. Since that force is not applied directly to the COM, it also applies a torque, which makes the car rotate forwards. The suspension at the front applies another torque upwards to fight against that twist (because the ground is in the way). You can feel the front end of the car dip when you brake. Then, when you stop braking and that force is no longer applied, the tires stop applying that torque to the car and the car feels like it rocks backwards as the suspension evens itself out. That's all torques being applied.

We agree here. Top of the car has a forward force, bottom of the car experiences a backward force via the braking. Both about the COM (somewhere in between). Result is a rotational flip. Since the forward force is still higher the car probably still globally travels forward. Sure, pretty basic.

1 hour ago, Ty_Webb said:

Ignoring the twist forces applied to the club leaves you way short of being able to describe the motion. Otherwise the orientation of the club would never change.

You really think there are deliberate twist forces applied? Like forcing the club head forward and simultaneously forcing grip end in the opposite direction? Heck I don't think we even slow down the grip end deliberately let alone force it the other way. Sorry, if I am missing something here. The orientation change is simple incidental because there is different rate of global movement of grip vs. clubhead throughout the swing. I also happen to think the best swings have the least amount of differential movement between the two end in the impact zone. 

2 hours ago, iacas said:

I think you're getting into the coupling point or the couple of the hands, but that's a different ball of wax.

In my defense, I never thought one could do justice in covering all aspects of a golf swing in a paragraphs or two to begin with. Especially not with grade school physics..😜

1 hour ago, iacas said:

Yeah.

I'm not sure what Vishal is really talking about with the "constrained" COM. The club's COM doesn't really change much. Less than the body's does…

We definitely apply force to the golf club to move it both translationally (linear force) and rotationally (torque) to the golf club.

That's what Manzella's alpha/beta/gamma is all about. Even before they switched the reference frame from the global to the club-based one. 😉 

Okay.

[iacas]

11 hours ago, GolfLug said:

You really think there are deliberate twist forces applied? Like forcing the club head forward and simultaneously forcing grip end in the opposite direction?

This is where stuff gets muddy, as we're only contacting the club well to one side of the club's COM (at the grip), but we can still apply forces that act both linearly and rotationally.

[GolfLug]

1 hour ago, iacas said:

This is where stuff gets muddy, as we're only contacting the club well to one side of the club's COM (at the grip), but we can still apply forces that act both linearly and rotationally.

I think we agree on what's actually happening. I got hung up on the force couple (when someone mentions torque, I instinctively look for one). Guess I'm being a bit nit-picky. My bad.

[GreenhornGolfer]

On 7/31/2025 at 6:28 PM, iacas said:

You can make a 9I as long as a driver and the driver is still going to hit the ball a lot farther.

Well yes as the length of the club is just one factor that contributes to the distance it will send the ball. There are other factors as well. For instance the head of the driver is made out of a material that is designed to send the ball further than the head of the nine iron. Also, the shaft of the driver is more flexible than that of the 9 iron which also contributes to the speed of the ball and thus the distance of the ball. 

On 7/31/2025 at 6:28 PM, iacas said:

The stuff about the clubhead rotating faster than the grip is very basic. Grade school physics.

Yes and I was wondering if there is a specific name for that scientific law, about how when you swing a stick (such as a golf club) how the end of the stick is going to be moving faster than where you're holding it because it has to cover more distance in the same amount of time. 

[Ty_Webb]

19 minutes ago, GreenhornGolfer said:

Well yes as the length of the club is just one factor that contributes to the distance it will send the ball. There are other factors as well. For instance the head of the driver is made out of a material that is designed to send the ball further than the head of the nine iron. Also, the shaft of the driver is more flexible than that of the 9 iron which also contributes to the speed of the ball and thus the distance of the ball. 

Far and away the biggest difference between 9 iron and driver is the loft. The straighter the face, the more energy is going to be passed to ball speed. Put another way, a 9 iron is going to have a much more glancing blow on the ball than a driver. At impact, energy and momentum both have to be conserved. The coefficient of restitution (COR) of the club is the bit that factors in the energy loss to other stuff (sound and heat mainly I think). The 0.830 max COR equates to about a 1.50 smash factor, so that's the limit. Less loft also means less launch and less spin, so while a 0* driver might have the highest ball speed (depending on your swing mechanics somewhat), it would also launch low and impart no spin and a golf ball that doesn't spin will not go very far (about 75 yards I think with ball speed that would go 300 yards if optimized). So driver loft is a balancing act. 9 iron is really about distance control, not distance and it wants to sit between 8 iron and wedge so that's what dictates that.

Golf ball aerodynamics is a pretty interesting study I think. Spin and dimples both help keep the ball in the air and moving freely. Spin gives the ball some lift to counteract gravity and dimples help to keep a little cushion of air around the ball, which is less disruptive to the air around it compared to a smooth ball. Significantly less turbulence behind the ball, which means less drag and therefore more distance. They originally discovered that back in the day because a ball that had been hit thin a few times and therefore had cuts in its surface would travel a lot further than a new clean round ball. 

[GolfLug]

1 hour ago, GreenhornGolfer said:

Yes and I was wondering if there is a specific name for that scientific law, about how when you swing a stick (such as a golf club) how the end of the stick is going to be moving faster than where you're holding it because it has to cover more distance in the same amount of time. 

It's called 'applying a moment to a lever'. All things considered equal, especially effective mass, further the business end of the lever from point of application of the moment, further it will travel compared to another point on the lever that is closer. It's all covered under something called the 'law of conservation of momentum'. The grip end is only a couple of inches from point of moment application, give or take, compared to the clubhead which is 40+ inches away. You do the math. In real life, this is why some golfers choke down on the grip a bit when they want hit it couple of yards shorter - to effectively reduce leverage. On the flip side long drivers use as long a shaft as they legally can.

@Ty_Webbis dead on about club loft and ball aerodynamics.

Edited August 5 by GolfLug

[iacas]

@GreenhornGolfer, please stop with the third-grade level physics. At its best, it's incredibly boring.

[boogielicious]

FWIW, and this is absolutely true, I did my first experiment for my class in kindergarten showing that heat rises and cold sinks with colored water. Does that make me a super nerd? I guess that’s kindergarten physics.

[billchao]

6 hours ago, boogielicious said:

Does that make me a super nerd?

Yes.