Physics

[p1n9183]

I really liked this videos. 

 

I wonder about how to effitiently apply force to the handle of the club on the downswing. 

Me personally used to apply force to the grip in the direction off the ball. I had a very steep angle of attack with my hands to the ball. 
After looking at this videos I started to apply force downwards in the beginning of the backswing and then towards the flag/target when I was about to hit the ball. 
After looking at pro players, they all start to lift their hands before hitting the ball. I don't know if it is because of pushing with their left leg up or because they apply force upwards to the grip when they reach the ball, or something else? 

 

[iacas]

1 hour ago, p1n9183 said:

Woof. Not good. 8:40 to 8:50, blah. I know the grip is turned a bit to the left in that part of the video (face is closed a bit), but… no. Not that.

[Ty_Webb]

On 7/21/2025 at 2:53 PM, iacas said:

I didn't say it was unfeasible.

That's not what you said. And… be careful there.

Not around the club's COM, man.

Okay - I'm going to try this again from the top. While that may not be what I said, it is what I meant, although it appears I didn't express it very clearly.

The hands apply forces and torques to the club throughout the swing. Any force applied to something like a club can be broken down into the portion of the force that is perpendicular to the shaft and the portion that is parallel to the shaft. The part that is perpendicular to it is applying a torque to the club, which will cause its rotation to change.

In a similar fashion, we can look at the club as the sum of two different sets of motion. One of those is how the COM of the club is moving through space. That is affected by all the forces applied to the club, be they from the hands or gravity or the ground or the ball or the air - I think that's about it. The hands in a full swing are going to be the vast majority of those forces. Then the change in location of the COM (translational motion I think it's called) is caused by the net of all the forces applying to it.

The perpendicular portion of the force is the only one that matters for rotational motion. That can be considered exclusive of the translational motion. Rotational motion will change with torques applied and can be contemplated on its own.

From P6 to P7, you start with the club lagging behind the hands. The hands then pull up (among other things), which is a force applied to the club, not directly through the COM of the club. That means that a torque is being applied to the club by the hands. One which will cause the club to rotate around its COM if we are exclusively looking at the rotational motion. And so, in that sense, the club is rotating around it's COM. That's the part of the motion that I was trying to describe originally. That upward force from the hands is also going to be accelerating the COM around the swing arc due to the net effect of the forces applied to it. 

Then, the combined effect of the forces and torques may be to cause the club to rotate around something else in a different reference frame. You can draw a line up the shaft of the club in each frame of video around impact and the point where those lines meet is roughly the center of rotation of the club in the static frame. That center of rotation is also moving through time as you'll see the point where the lines meet is rarely going to remain in the same spot. In any case, this is a different rotation from what I was trying to talk about previously. 

[iacas]

5 minutes ago, Ty_Webb said:

The part that is perpendicular to it is applying a torque to the club, which will cause its rotation to change.

That's not always true. I can apply a force perpendicular to the club… through the center of mass. No rotation.

😉

5 minutes ago, Ty_Webb said:

That can be considered exclusive of the translational motion. Rotational motion will change with torques applied and can be contemplated on its own.

You don't "apply" a torque. A torque is a result of the force away from the COM. And, per the above, it's not exclusive of the translational motion. Nit-picky, yes. But if we're gonna talk about physics, let's actually talk about physics, and not the ninth grade version of it.

5 minutes ago, Ty_Webb said:

From P6 to P7, you start with the club lagging behind the hands.

I know what you mean, but again, getting terminology right is a big part of this. It's not "behind" the hands exactly as it's already kicked out a little (mostly at that point because  the hands have already slowed a little).

5 minutes ago, Ty_Webb said:

The hands then pull up (among other things), which is a force applied to the club, not directly through the COM of the club.

They don't really pull up much. They just continue around their arc. The upward pulling here is small. You've seen resultant forces, but may be confusing "holding onto the grip" with how much the hands actually pull upward. To say it another way, you may be confusing the force and the counter force that stops the club from slipping out of your hands.

5 minutes ago, Ty_Webb said:

One which will cause the club to rotate around its COM if we are exclusively looking at the rotational motion.

No, because that would be a silly way to look at it given that the golfer is not only holding onto the club  but continuing to push the handle forward, too.

5 minutes ago, Ty_Webb said:

That's the part of the motion that I was trying to describe originally.

Poorly, yes.

5 minutes ago, Ty_Webb said:

That upward force from the hands

See above.

[GreenhornGolfer]

So with all this talk about physics and the speed of the club and the speed of the ball and so forth, I would like to say something in regards to speed and Im looking for feedback on whether Im right about this. As I said before Im new to golf and while I've got a little bit of a background in physics, there are some people on this forum who know much more about physics than I do. 

So what Im going to say about speed is this, speed directly correlates to distance. There are other factors that determine the distance the ball will go such as trajectory but with all other factors being equal, a faster ball will go further. So in that sense we can say speed equals distance when all the other factors are the same. 

The reasons for this is because distance equals speed multiplied by time which means a faster ball will go further in the same amount of time that it takes gravity to cause the ball to come to the ground. Also, a faster ball will be better at overcoming air resistance which will also enable it to go further. 

With a faster ball going further, that's why the driver is the longest club, its designed to hit the ball the furthest and being the longest club, it has the most torque so the club head is moving the fastest, faster than with other clubs, when it hits the ball and transfers its speed to the ball. 

So this is my best understanding about speed and how it affects distance, so Im just looking for feedback to see if Im right.

[Ty_Webb]

18 hours ago, iacas said:

That's not always true. I can apply a force perpendicular to the club… through the center of mass. No rotation.

😉

Yes - true. How many times do you do that in a golf swing?

18 hours ago, iacas said:

You don't "apply" a torque. A torque is a result of the force away from the COM. And, per the above, it's not exclusive of the translational motion. Nit-picky, yes. But if we're gonna talk about physics, let's actually talk about physics, and not the ninth grade version of it.

I think most levels of physics (certainly mine up to and including at university) separated the components to make them easier to handle. We can talk about the translational piece too if you want to.  

18 hours ago, iacas said:

I know what you mean, but again, getting terminology right is a big part of this. It's not "behind" the hands exactly as it's already kicked out a little (mostly at that point because  the hands have already slowed a little).

I'm talking about a face on view. The hands are closer to the target than the clubhead, so it's behind.

18 hours ago, iacas said:

No, because that would be a silly way to look at it given that the golfer is not only holding onto the club  but continuing to push the handle forward, too.

At impact, what's the net force on the handle and in what direction? 

 

 

 

 

 

 

[saevel25]

21 hours ago, iacas said:

You don't "apply" a torque. A torque is a result of the force away from the COM. And, per the above, it's not exclusive of the translational motion. Nit-picky, yes. But if we're gonna talk about physics, let's actually talk about physics, and not the ninth grade version of it.

Yea, when talking physics, definitions matter. Being technically correct matters. 

21 hours ago, iacas said:

To say it another way, you may be confusing the force and the counter force that stops the club from slipping out of your hands.

Yea, if the club is being sent outwards from its center of rotation at 100 lbs, then if it isn't slipping out of your hands the hands are holding onto it with at least 100 lbs. 

2 hours ago, GreenhornGolfer said:

So in that sense we can say speed equals distance when all the other factors are the same. 

Kind off, but slower swing speeds need more spin to maximize carry. So, in terms of carry distance, things all being equal isn't really true. 

2 hours ago, GreenhornGolfer said:

With a faster ball going further, that's why the driver is the longest club, its designed to hit the ball the furthest and being the longest club, it has the most torque so the club head is moving the fastest, faster than with other clubs, when it hits the ball and transfers its speed to the ball. 

Not necessarily, 

Torque = r * 2 * Pi * v

v = rotational velocity

You could have the same torque with a driver and 3-wood, but the velocity of the driver is just proportional to the radius change. Since you would have. 

r1 * 2 * pi * v1 = r2 * 2 * pi * v2

v1 = v1 * (r2 / r1). 

I picked 3 wood and driver because they could be similar in weight, so you would apply similar forces. 

2 hours ago, Ty_Webb said:

I'm talking about a face on view. The hands are closer to the target than the clubhead, so it's behind.

Yea, but it's on an arc. So, the swings would be represented with three vectors, not two. It maybe simple to look at face-on (2-d), but it's not accurate. 

 

[Ty_Webb]

33 minutes ago, saevel25 said:

Yea, but it's on an arc. So, the swings would be represented with three vectors, not two. It maybe simple to look at face-on (2-d), but it's not accurate. 

I don't disagree with you, but I was explaining to Erik that I meant from face on rather than down the line. He said the club has started to kick out and is not behind the hands. Down the line that's true (so I assume that's what he meant), but face on, which is what I was talking about, it's not. Is it your position that the clubhead at P6 is not behind the hands from face on? At P6, the clubshaft is horizontal. By impact it has to be a whole lot closer to vertical, so it has to rotate. The hands therefore have to cause it to rotate. Can do that in a few ways. Top hand can push backwards while the bottom hand pushes forwards, but I don't think that's what's happening since someone a lot smarter than I am posted a few pictures of Phil and Vijay with their bottom hands virtually off the club at impact. So that leaves the top hands pushing backwards, but that seems to me like it would be counterproductive seeing as we are trying to speed the clubhead up. Or the hands pull up, which when the club is not in a straight line with them (see e.g. P6) imparts a torque on the club which causes it to rotate. I imagine that there is a little bit of both going on really, but given the bottom hand off the club pictures I think the pulling inwards towards the body center (I said up before, but you're right it should be 3-d) is a fairly significant portion of the force on the club that causes it to rotate.

On 7/18/2025 at 4:01 PM, saevel25 said:

Some front driven cars now have front differentials. Mostly on more performance cars. It helps a lot with oversteering and understeering. 

 

Car question. If you want to improve a car's acceleration by removing weight, what weight is the best to reduce to accomplish that?

[saevel25]

12 minutes ago, Ty_Webb said:

Car question. If you want to improve a car's acceleration by removing weight, what weight is the best to reduce to accomplish that?

Wheel weight. It’s the physical mass of the wheel will resist rotation. Lighter wheels will have higher rotational acceleration.

though you probably could remove a lot more weight from the body and the car seats, which would in terms of total mass could exceed what you could do by getting lighter wheels.

 

[Ty_Webb]

6 minutes ago, saevel25 said:

Wheel weight. It’s the physical mass of the wheel will resist rotation. Lighter wheels will have higher rotational acceleration.

though you probably could remove a lot more weight from the body and the car seats, which would in terms of total mass could exceed what you could do by getting lighter wheels.

 

I meant lb for lb - so yes I agree it's wheel weight. How would you go about explaining that to someone? Perhaps the rotational inertia being higher with heavier wheels and the rotational inertia of the wheel requiring more torque to make its angular acceleration increase at the same rate? 

[iacas]

9 hours ago, GreenhornGolfer said:

So this is my best understanding about speed and how it affects distance, so Im just looking for feedback to see if Im right.

Yes, a ball going faster will go farther… but it's nearly impossible for "all other parameters" to remain the same.

"A ball going faster with the same of everything else will go farther" is pretty rudimentary stuff.

9 hours ago, Ty_Webb said:

Yes - true. How many times do you do that in a golf swing?

The entire swing. The handle moves the whole time. The golf swing is a matter of both translational and rotational forces.

9 hours ago, Ty_Webb said:

I'm talking about a face on view. The hands are closer to the target than the clubhead, so it's behind.

And yet it's also kicked out a little, as it's not directly behind the motion of the hand path at that instant.

[GolfLug]

7 hours ago, saevel25 said:

Wheel weight. It’s the physical mass of the wheel will resist rotation. Lighter wheels will have higher rotational acceleration.

though you probably could remove a lot more weight from the body and the car seats, which would in terms of total mass could exceed what you could do by getting lighter wheels.

 

I would start with the car roof and body panels the work my way to components closest to the ground. Reduce peripheral/distal weight to reduce torque demand. Wheels would be last on my list. 

F1 cars weigh 40%of normal street cars but their wheels weigh maybe 80% of the normal car wheels.

7 hours ago, Ty_Webb said:

I meant lb for lb - so yes I agree it's wheel weight. How would you go about explaining that to someone? Perhaps the rotational inertia being higher with heavier wheels and the rotational inertia of the wheel requiring more torque to make its angular acceleration increase at the same rate? 

Rotational inertia of a wheel/tire only matters if the load it's propelling is low like its own weight or less. It matters very little to none for the amount of load it carries in case of cars (100X or more..). 

[GreenhornGolfer]

3 hours ago, iacas said:

"A ball going faster with the same of everything else will go farther" is pretty rudimentary stuff.

Right, well what Im trying to say is that distance is directionally proportional to speed. 

[iacas]

7 hours ago, GreenhornGolfer said:

Right, well what Im trying to say is that distance is directionally proportional to speed. 

Yes, it’s very rudimentary stuff. It went without saying.

I think you meant directly.

[GreenhornGolfer]

2 hours ago, iacas said:

Yes, it’s very rudimentary stuff. It went without saying.

I think you meant directly.

Yes I meant to say directly, it looks like it's too late to edit the post. 

[GreenhornGolfer]

So there's been some really interesting discussions going on here about how various aspects of physics apply to golf and particularly about how the head of a golf club will be moving faster than the grip when you swing it because it has to cover more distance in the same amount of time. 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. Other interesting facts have been stated as well, such as how you want your hands to be moving at maximum speed not when the club impacts the ball but before the club impacts the ball because the club head reaches its maximum speed after your hands reach their maximum speed, not during. 

 

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. 

[Ty_Webb]

25 minutes ago, GreenhornGolfer said:

So there's been some really interesting discussions going on here about how various aspects of physics apply to golf and particularly about how the head of a golf club will be moving faster than the grip when you swing it because it has to cover more distance in the same amount of time. 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. Other interesting facts have been stated as well, such as how you want your hands to be moving at maximum speed not when the club impacts the ball but before the club impacts the ball because the club head reaches its maximum speed after your hands reach their maximum speed, not during. 

 

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. 

The main difference I think is that in golf, the club hits the ball and the ball leaves at a higher speed than the club was traveling (with most of your clubs anyway), so 100mph clubhead speed can get up to around 150mph of ball speed with a driver. In baseball, something similar is true for the hitter, but there is no mechanism (that I'm aware of) for the ball to leave the pitcher's hand at any speed faster than the hand itself is traveling. Of course, the other point is that the club is quite a bit heavier than a baseball, so there is less resistance to overcome, so hand speeds up around 100mph are I guess feasible for top pitchers. At least the part of the hand that is in contact with the ball. You also have two hands on the club and that would mean that you have two hands and arms to accelerate vs the pitcher who only has to accelerate one hand. There must also be some rotational inertia to combat with the golf club that isn't there to any great extent with the baseball. If you try to throw a golf club overhead like you'd throw a ball, a lot of energy would go into moving it around you, unless you threw it like a javelin, but then you'd run a not inconsiderable risk of catching a clubhead to the back of the head and who would want that.

[saevel25]

50 minutes ago, GreenhornGolfer said:

It's interesting to see how physics applies to golf and then how it applies to other sports. 

A quick google search for baseball kinematics. 

Understanding the Kinematic Sequence • RPP Baseball

 

Edited July 31 by saevel25