# Speed from the Arms in the Golf Swing

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6 hours ago, iacas said:

Those calculations ignore two things:

• The club shaft and left arm are almost never straight. The distance from the left shoulder to the clubhead is rarely 67", and is only 67" for a fleeting moment in a golf swing.
• The club accelerates, it isn't traveling the arc of that thing at a constant speed. It's accelerating from 0 MPH.

You are absolutely correct on your first point. the wrist and elbow will bend, so the path of the swing is not an exact circle it is a combination of the circumferences of three circles whose centres are the wrist, elbow and sternum respectively. The example i gave above above is simplified but is close enough to make no difference.  The speed difference that Mike Malaska shows above is directly related to the length of the path of the tip of the speed stick. It says nothing about how that speed is generated.

In your second point, Acceleration is not relevant. Acceleration is  a function of speed, not the other way around. Acceleration is defined as the rate of change of speed between two points It is a calculated result of speed, which is itself a calculated result of two measured variables: distance and time.

The speed is clearly not constant through the swing as it goes from 0 to impact speed. Acceleration may or may not be constant throughout the path, The speed at impact is the speed at impact and it is completely independent of the acceleration profile between top of the backswing and impact

I am going to go back to the simplified driver example. Yes I know its not exactly a golf swing but it is close enough to explain the point.

For a circle with a 67" radius (22" arms and 45" clublength) the circumferance is 2*pi*r in this case its 421". if we take the swing from top of back swing to impact, that is half the circumference which is 210.5".

If the swing takes 0.25 seconds to complete from the top, then it takes 0.125 to go from top to impact. (Again this may vary slightly based on tempo, but I think its a reasonable approximation for the purpose of this example.)

So the two measured variables are distance: 210" and time 0.125 seconds and we make the reasonable assumption that the club is not moving at the top of the backswing: (initial speed =0). Speed = initial speed + distance /time. The speed of the clubhead at impact is 0 + 210.5"/0.125 seconds = 0.003322083 miles / 0.000034722 hours = 95.7 mph.

From these values we can also calculate the average acceleration of the club from top to impact. it is 95-0 miles per hour. divided by 0.125 seconds or 0.000034722 hours. That give a pretty impressive 2755468.8mp(h)^2

If you wanted to look at acceleration between smaller distances along the path, you would have to measure the distances & measure the time between them. you can then calculate the speed and acceleration at various points along the swing. This as you know can be and is done using high speed cameras.

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1 hour ago, smdillon said:

The example i gave above above is simplified but is close enough to make no difference.  The speed difference that Mike Malaska shows above is directly related to the length of the path of the tip of the speed stick. It says nothing about how that speed is generated.

I don't understand what you're saying. He's swinging one of them like this:

and the other like this:

It's not the best demonstration because he's still turning his shoulders back in the second one, but it's clearly about more than just the difference in the radius.

1 hour ago, smdillon said:

In your second point, Acceleration is not relevant. Acceleration is  a function of speed, not the other way around. Acceleration is defined as the rate of change of speed between two points It is a calculated result of speed, which is itself a calculated result of two measured variables: distance and time.

Acceleration is entirely relevant, because your calculation has to take into account the acceleration of the clubhead. Given the time and radius, sure you can figure out the distance the clubhead travels and ballpark a clubhead speed… but you absolutely need to realize and account for the fact that the speed is changing (and non-linearly) over that time period and distance.

1 hour ago, smdillon said:

For a circle with a 67" radius (22" arms and 45" clublength) the circumferance is 2*pi*r in this case its 421". if we take the swing from top of back swing to impact, that is half the circumference which is 210.5".

This clubhead is traveling more than 210" and the radius from the left shoulder to the clubhead is nowhere near 67":

1 hour ago, smdillon said:

So the two measured variables are distance: 210" and time 0.125 seconds and we make the reasonable assumption that the club is not moving at the top of the backswing: (initial speed =0). Speed = initial speed + distance /time. The speed of the clubhead at impact is 0 + 210.5"/0.125 seconds = 0.003322083 miles / 0.000034722 hours = 95.7 mph.

What? Dude.

All you've done there is take the distance traveled (210.5") and divide it by the time (0.125 seconds)… which assumes a constant velocity.

You've literally taken a distance and divided it by a time, which will give you an average speed, and you're concluding it's the final speed.

Then the rest of your math "builds" on that faulty bit.

You don't know the final velocity OR the acceleration rate, so you can't solve for the other one, and you're assuming acceleration is linear (it's not) and that the clubhead travels only half of the arc (it travels much more for most golfers, while the left arm travels less).

So please, let's stop with the faux/faulty math.

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Posted (edited)
49 minutes ago, iacas said:

I don't understand what you're saying. He's swinging one of them like this:

and the other like this:

It's not the best demonstration because he's still turning his shoulders back in the second one, but it's clearly about more than just the difference in the radius.

Acceleration is entirely relevant, because your calculation has to take into account the acceleration of the clubhead. Given the time and radius, sure you can figure out the distance the clubhead travels and ballpark a clubhead speed… but you absolutely need to realize and account for the fact that the speed is changing (and non-linearly) over that time period and distance.

This clubhead is traveling more than 210" and the radius from the left shoulder to the clubhead is nowhere near 67":

What? Dude.

All you've done there is take the distance traveled (210.5") and divide it by the time (0.125 seconds)… which assumes a constant velocity.

You've literally taken a distance and divided it by a time, which will give you an average speed, and you're concluding it's the final speed.

Then the rest of your math "builds" on that faulty bit.

As i said mine was a simplified model for example purposes.

The mathematical basics are very simple. Speed is a function of distance and time. Nothing else.

The 2 only things that define clubhead speed at impact are: 1) the distance that the club head travels from top to impact. and 2) the time it takes to travel that distance.  Nothing else. speed = initial speed + distance/time.that's the mathematical definition of speed. I think we agree that the there is a point at the top of the backwing that the club is not moving, so initial speed = 0.

it is important to remember acceleration is a calculated function of speed not the other way around. Acceleration is dependent on speed, speed is not dependent on acceleration.

What Mike Malaska has done with his arm speed example is to dramatically increase the distance that the tip of the speed stick travels by increasing the radius via arm length. Since speed is calculated as distance/time and the time taken is the same, the speed dramatically increases. Also, since acceleration is a function of speed ((delta speed)/time) then he has also increased acceleration.

He has done this simple by increasing the basic radius of his arc. Nothing else.

It's the same principle as to why a driver clubhead speed is faster than a 7 iron clubhead speed for the same player.

Edited by

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1 minute ago, smdillon said:

As i said mine was a simplified model for example purposes.

They're so simplified (read: wrong) that they don't serve any real purpose except to distract the conversation into an area where we have to spend time pointing out how bad your "models" are.

1 minute ago, smdillon said:

The mathematical basics are very simple. Speed is a function of distance and time. Nothing else.

The speed is not a constant.

Despite some people acting like I say this all the time, I don't, but it works here: you're wrong.

1 minute ago, smdillon said:

The 2 only things that define clubhead speed at impact are: 1) the distance that the club head travels from top to impact. and 2) the time it takes to travel that distance.  Nothing else. speed = initial speed + distance/time.that's the mathematical definition of speed. I think we agree that the there is a point at the top of the backwing that the club is not moving, so initial speed = 0.

Dude, I can't make this simpler for you: it accelerates from 0. It's not traveling at a constant speed.

6 minutes ago, smdillon said:

He has done this simple by increasing the basic radius of his arc. Nothing else.

He's also increased the size of that arc.

Stop using really bad math to "prove" whatever point it is you're trying to make.

1 minute ago, smdillon said:

it is important to remember acceleration is a calculated function of speed not the other way around. Acceleration is dependent on speed, speed is not dependent on acceleration.

Speed is dependent on acceleration, too.

I'm ignoring the rest of what you've written because I've realized I'm just repeating myself, and you're just repeating yourself, and you're clearly wrong. I get to say "you're wrong" here because we're not talking about matters of opinion, but matters of fact. Your math is wrong. No more from you on this please.

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16 minutes ago, smdillon said:

As i said mine was a simplified model for example purposes.

The mathematical basics are very simple. Speed is a function of distance and time. Nothing else.

The 2 only things that define clubhead speed at impact are: 1) the distance that the club head travels from top to impact. and 2) the time it takes to travel that distance.  Nothing else. speed = initial speed + distance/time.that's the mathematical definition of speed. I think we agree that the there is a point at the top of the backwing that the club is not moving, so initial speed = 0.

it is important to remember acceleration is a calculated function of speed not the other way around. Acceleration is dependent on speed, speed is not dependent on acceleration.

What Mike Malaska has done with his arm speed example is to dramatically increase the distance that the tip of the speed stick travels by increasing the radius via arm length. Since speed is calculated as distance/time and the time taken is the same, the speed dramatically increases. Also, since acceleration is a function of speed ((delta speed)/time) then he has also increased acceleration.

He has done this simple by increasing the basic radius of his arc. Nothing else.

It's the same principle as to why a driver clubhead speed is faster than a 7 iron clubhead speed for the same player.

This math is faulty. This is not a train on a track that has constant acceleration. There are many more components and this simplification creates errors. Also, we are talking about velocity, not speed. I recommend you search for how to calculate rotational velocity and add from a stationary start like a propeller tip or something. Also, the club head doesn’t travel in a perfect circle either. The radius increases during the swing.

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4 minutes ago, iacas said:

They're so simplified (read: wrong) that they don't serve any real purpose except to distract the conversation into an area where we have to spend time pointing out how bad your "models" are.

The speed is not a constant.

Despite some people acting like I say this all the time, I don't, but it works here: you're wrong.

Dude, I can't make this simpler for you: it accelerates from 0. It's not traveling at a constant speed.

Speed is dependent on acceleration, too.

I'm ignoring the rest of what you've written because I've realized I'm just repeating myself, and you're just repeating yourself, and you're clearly wrong.

I never said the club travelled at a constant speed. It clearly doesn't

The fact that acceleration is a function of speed is not a matter of opinion. it is a scientific definition, Acceleration is defined as the rate of change of speed.

Speed is completely independent of acceleration that is a categorical mathematical and scientific fact. If you don't believe me, speak too someone you know who has a scientific or mathematical qualification. Speed is defined as initial speed + distance/ time. It has no dependence on acceleration whatsoever.  Acceleration is defined as the rate of change of speed. It has no existence outside of that definition. Since acceleration defined as function of speed, it is physically not possible for speed to be a function of acceleration.

I have a degree in engineering, and this is applied maths 101.

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1 minute ago, smdillon said:

I never said the club travelled at a constant speed. It clearly doesn't

The fact that acceleration is a function of speed is not a matter of opinion. it is a scientific definition, Acceleration is defined as the rate of change of speed.

Speed is completely independent of acceleration that is a categorical mathematical and scientific fact. If you don't believe me, speak too someone you know who has a scientific or mathematical qualification. Speed is defined as initial speed + distance/ time. It has no dependence on acceleration whatsoever.  Acceleration is defined as the rate of change of speed. It has no existence outside of that definition. Since acceleration defined as function of speed, it is physically not possible for speed to be a function of acceleration.

I have a degree in engineering, and this is applied maths 101.

They should revoke your degree. Let me make this very simple by pointing out one of the many flaws, perhaps the most basic: you calculated distance/time (210.5"/0.125s), which gives you an AVERAGE speed.

If I leave my house and pass a sign on the highway five miles away after 10 minutes, I can calculate my average speed to that point (30 MPH), but that doesn't mean I'm traveling 30 MPH when I pass that sign.

1 minute ago, smdillon said:

Speed is defined as initial speed + distance/ time.

No, it's not, and if the initial speed is zero, you're only finding the average speed. Speed is the instantaneous measure of distance over time. Add in the direction and you can call it velocity (which is why something swinging at a constant linear speed is still "accelerating" when it's turning/curving), but you're completely ignoring that the clubhead accelerates the entire downswing with your bogus math.

No more posts from you on this topic, by rule, unless it's a full "oh my gosh, what a brain fart, I'm so sorry" type of thing.

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1 minute ago, boogielicious said:

This math is faulty. This is not a train on a track that has constant acceleration. There are many more components and this simplification creates errors. Also, we are talking about velocity, not speed. I recommend you search for how to calculate rotational velocity and add from a stationary start like a propeller tip or something. Also, the club head doesn’t travel in a perfect circle either. The radius increases during the swing.

The maths is not fault. the maths is very basic and correct. "Speed" and  "velocity" are interchangeable, I used the word speed to keep it simple for people.

Speed of the clubhead at impact is the distance that the clubhead  travels from the top of the swing where speed =0 to the point of impact, divided by the time between those to point. that is basic maths or math as its know as on your side of the Atlantic.

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3 minutes ago, smdillon said:

Speed of the clubhead at impact is the distance that the clubhead  travels from the top of the swing where speed =0 to the point of impact, divided by the time between those to point.

No, it isn't.

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13 minutes ago, smdillon said:

I never said the club travelled at a constant speed. It clearly doesn't

The fact that acceleration is a function of speed is not a matter of opinion. it is a scientific definition, Acceleration is defined as the rate of change of speed.

Speed is completely independent of acceleration that is a categorical mathematical and scientific fact. If you don't believe me, speak too someone you know who has a scientific or mathematical qualification. Speed is defined as initial speed + distance/ time. It has no dependence on acceleration whatsoever.  Acceleration is defined as the rate of change of speed. It has no existence outside of that definition. Since acceleration defined as function of speed, it is physically not possible for speed to be a function of acceleration.

I have a degree in engineering, and this is applied maths 101.

If we’re playing that game, I have a Masters in Chemical Engineering and 40 years experience. You would have failed basic physics with these simplifications. You are thinking linearly not rotationally. You are thinking mean and not point velocity and not in the correct coordinates or breaking velocity into its vector components. All this leads to faulty maths.

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4 minutes ago, boogielicious said:

You are thinking mean and not point velocity

Yep. The most egregious and basic of your errors.

Our moderation team has roughly eight scientific degrees, and many of us have taken advanced physics classes, as well as other advanced science classes.

Nobody is saying you aren't getting the right answer for 210.5/0.125. What we're pointing out is that you're using the entirely wrong formula. It's worthless in this context, and gives you an average speed.

You're wrong here, @smdillon, and if you're man enough (smart enough?) to admit it, we can all move on.

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32 minutes ago, smdillon said:

Speed is completely independent of acceleration that is a categorical mathematical and scientific fact. If you don't believe me, speak too someone you know who has a scientific or mathematical qualification. Speed is defined as initial speed + distance/ time. It has no dependence on acceleration whatsoever.  Acceleration is defined as the rate of change of speed. It has no existence outside of that definition. Since acceleration defined as function of speed, it is physically not possible for speed to be a function of acceleration.

I have a degree in engineering, and this is applied maths 101.

It is very sad that you are actually an Engineer.

The analogy of what is going on here is a crash testing car. They are at zero velocity at the start line. They punch the accelerator and the car quickly gets up to maximum speed before slamming into a wall.

It is true you can use your equation to calculate a speed relative to the total distance they are traveling. That means nothing when you ask the question, what is the maximum speed? Or, what is the speed when the car hits the wall?

At point zero the speed is zero. At a point half a second later the speed could be 15 mph. At a point 1 second later it could be 30 mph. At a point 6 seconds later it could be 70 mph. Then the car hits the wall.

A golf ball only cares what the clubhead speed is at impact. It doesn't care what the average speed was over the duration of the arc.

When a police officer pulls you over for speeding, do you crunch the numbers for him taking into account all the stop signs you need to stop at or changes in speed due to speed limit changes? Not, the cop uses a radar gun an gets your speed at a very small moment in time.

37 minutes ago, iacas said:

No, it's not, and if the initial speed is zero, you're only finding the average speed. Speed is the instantaneous measure of distance over time. Add in the direction and you can call it velocity (which is why something swinging at a constant linear speed is still "accelerating" when it's turning/curving), but you're completely ignoring that the clubhead accelerates the entire downswing with your bogus math.

This^

I can still remember the physics teacher at Ohio State going through how the equations were derived. It made sense to me because it matched up with my calculus class when finding derivatives.

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7 hours ago, smdillon said:

What Mike Malaska has done with his arm speed example is to dramatically increase the distance that the tip of the speed stick travels by increasing the radius via arm length. Since speed is calculated as distance/time and the time taken is the same, the speed dramatically increases. Also, since acceleration is a function of speed ((delta speed)/time) then he has also increased acceleration.

He has done this simple by increasing the basic radius of his arc. Nothing else.

Regardless of faulty math (I'll let everyone else talk to that), I'm not sure how you could watch that video and get that impression.

Grab an alignment stick and do his demo, but when you do the "arms only" swing, grip halfway down on the stick.

I'm doing it right now - it's still be moving much much faster than the other swing types.

The other thing you can do is hold the stick in your hands like normal and swing via the different methods. You should still find that the "arms only" swing is the fastest.

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I hold a driver clubhead out the window of a 10-story building (and in a vacuum). I release the clubhead as you start a timer. After one second, the clubhead has traveled how many meters downward, and what speed is it traveling after one second?

Hint: the answers are not the same.

P.S. And I'm not just talking about the units, as one will be in m and the other will be in m/s.

3 minutes ago, jamo said:

The other thing you can do is hold the stick in your hands like normal and swing via the different methods. You should still find that the "arms only" swing is the fastest.

Yep.

Much like some of the earlier videos in this topic, too.

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I'm a freaking Spanish teacher and I know the maths are wrong for that guy lol....or should I say "jajajajaja"

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3 hours ago, colin007 said:

I'm a freaking Spanish teacher and I know the maths are wrong for that guy lol....or should I say "jajajajaja"

Señor Colin, tengo problemas con las matemáticas y necesito ayuda.

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So, is Mike Malaska correct, incorrect, or only speaking about part of the picture (over simplifying) as regards swing speed? Thanks.

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Go back to the OP and earlier posts.

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