First one: the definition of acceleration. Homer says:
"A change in the product of Mass times Velocity"
Fact:
Mass times velocity = momentum
Change in mass times velocity = change in momentum = impulse
Base units for acceleration is meters per seconds squared, whereas base units for momentum and impulse is kilograms meters per second. They are two completely different concepts.
So the definition is just plain wrong. I tried to make an excuse for Homer, but I couldn't find one!
I hope somone can give me a good explanation for this! I want to think that I am the one who has this wrong, because I can't imagine Homer making such a basic mistake.
Homer is not God, thus is not infallible...remember in his time, he did not have microsoft XP to do his publishing...
Not a valid excuse since, for whatever reason, it has not been corrected in the 7th edition.
How can one confuse the concept of impulse and acceleration. Such an un-Homer thing to do.
Still awaiting for a good reason, maybe Yoda? I remember Yoda saying that there are no factual errors in The Golfing Machine (although certain concepts may be expressed a lot more clearly). If this isn't a factual error, then...
First one: the definition of acceleration. Homer says:
"A change in the product of Mass times Velocity"
Fact:
Mass times velocity = momentum
Change in mass times velocity = change in momentum = impulse
Base units for acceleration is meters per seconds squared, whereas base units for momentum and impulse is kilograms meters per second. They are two completely different concepts.
So the definition is just plain wrong. I tried to make an excuse for Homer, but I couldn't find one!
I hope somone can give me a good explanation for this! I want to think that I am the one who has this wrong, because I can't imagine Homer making such a basic mistake.
A moving body has momentum (mass times velocity). There will be no change in this momentum until an outside force is applied to the object.
An impulse describes how this change in momentum occurs, with the amount of force and the length of time it is applied determining the ultimate effect. And any such change in that momentum, i.e., a change in either mass or velocity, will result in the acceleration (or deceleration) of that moving body.
Acceleration = the rate at which an object (e.g, the "mass" of the clubhead) changes its velocity.
So, an object (the "mass" of the clubhead) is accelerating if it is changing and increasing its velocity.
Therefore, any positive change in the product of mass x velocity(Homer's terminology) = acceleration; whereas any negative change would = deceleration.
First one: the definition of acceleration. Homer says:
"A change in the product of Mass times Velocity"
Fact:
Mass times velocity = momentum
Change in mass times velocity = change in momentum = impulse
Base units for acceleration is meters per seconds squared, whereas base units for momentum and impulse is kilograms meters per second. They are two completely different concepts.
So the definition is just plain wrong. I tried to make an excuse for Homer, but I couldn't find one!
I hope somone can give me a good explanation for this! I want to think that I am the one who has this wrong, because I can't imagine Homer making such a basic mistake.
A moving body has momentum (mass times velocity). There will be no change in this momentum until an outside force is applied to the object.
An impulse describes how this change in momentum occurs, with the amount of force and the length of time it is applied determining the ultimate effect. And any such change in that momentum, i.e., a change in either mass or velocity, will result in the acceleration (or deceleration) of that moving body.
What you said is correct Yoda, but just because impulse results in an acceleration doesn't meant it is acceleration. The definition of acceleration given in the glossary is wrong. Which is bad IMO.
But fortunately, for golfing purposes, mass (I am talking about mass in the usual sense as in mass mass, not effective mass) is constant, therefore impulse and acceleration is one to one related.
Also, most people understand acceleration better than impulse so that's another reason.
But I hope they change that definition in the 7th edition, and add another definition for impulse. Impact physics is about impulse, not just acceleration.
Good eye tongzilla. I did not like to see that "definition" of acceleration either - once you pointed it out. Hope to see changed. IMO it is one of those things that might be used to discredit the book or make people think less of it.
Good eye tongzilla. I did not like to see that "definition" of acceleration either - once you pointed it out. Hope to see changed. IMO it is one of those things that might be used to discredit the book or make people think less of it.
Well, here's how I found this unforgivable error.
I was showing a golfing friend about TGM, going on about how amazing it is, it's the bible, etc, etc...
And the guy has a physics background, and was scanning through the book, complaining about how badly laid out it was (well, I get that the whole time, and I understand the genius in laying out the book as it is, so I could deal with that!). But then, he told me there's a factual error in the book. My immediate reaction is there is never a factual error in TGM, just concepts you don't understand yet. But after taking a real look and giving a bit of real thought, the nightmare has come true! Homer has indeed got it wrong! That was slightlyembarassing for me...
So I totally agree with you Metallion, I don't want people to discredit Homer's work just because of a definition error. But some people do. They think, "Why listen to a guy who doesn't even know what's acceleration?"That would be a big shame. But this is a serious error and do have serious conceptual implications. Error must be corrected!
First one: the definition of acceleration. Homer says:
"A change in the product of Mass times Velocity"
Fact:
Mass times velocity = momentum
Change in mass times velocity = change in momentum = impulse
Base units for acceleration is meters per seconds squared, whereas base units for momentum and impulse is kilograms meters per second. They are two completely different concepts.
So the definition is just plain wrong. I tried to make an excuse for Homer, but I couldn't find one!
I hope somone can give me a good explanation for this! I want to think that I am the one who has this wrong, because I can't imagine Homer making such a basic mistake.
A moving body has momentum (mass times velocity). There will be no change in this momentum until an outside force is applied to the object.
An impulse describes how this change in momentum occurs, with the amount of force and the length of time it is applied determining the ultimate effect. And any such change in that momentum, i.e., a change in either mass or velocity, will result in the acceleration (or deceleration) of that moving body.
What you said is correct Yoda, but just because impulse results in an acceleration doesn't meant it is acceleration. The definition of acceleration given in the glossary is wrong. Which is bad IMO.
But fortunately, for golfing purposes, mass (I am talking about mass in the usual sense as in mass mass, not effective mass) is constant, therefore impulse and acceleration is one to one related.
Also, most people understand acceleration better than impulse so that's another reason.
But I hope they change that definition in the 7th edition, and add another definition for impulse. Impact physics is about impulse, not just acceleration.
When writing The Golfing Machine -- scientifically strictly a layman's text -- Homer Kelley was not attempting a doctoral thesis in Physics, and he stated that right up front (1-H):
"As a term is specifically defined herein, that is the basic connotation which is always a dictionary definition but not necessarily that of Physics, Electrical, etc. And the dictionary is generally considered a standard of precision...Clarity and usefulness are the only motive." [Bold by Yoda.]
One of my old Webster's definitions for acceleration is: "Change in the velocity of a moving body or the rate of such change. ' In G.O.L.F. we are dealing with the Angular Momentum -- mass and velocity -- of the moving Clubhead. And any force that changes that Momentum -- that increases or decreases it -- is an Accelerating Force (for example, Clubhead Lag Pressure) or a Decelerating Force (the violence of the Impact Collision).
And that is what Homer was saying.
Now, if you really want to see -- and hear! -- the practical effect of this knowledge, just use your Flat Left Wrist to stop the Clubhead quickly after Impact on a sharply hit Chip or Pitch Shot. The increased Acceleration Rate (Lag Pressure) increases the Effective Mass of the Clubhead (and consequently the 'product of mass times velocity').
Linear Mode
