Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby cdobe on Wed Dec 14, 2011 3:04 pm

With all due respect Fong, but you are wrong here. Vectors are abstract mathematical objects only. Forces exist in the real world. I don't think that's debatable, unless you advocate some whack idealistic philosophy.
I'm more than willing to put my statement under scrutiny...
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby nianfong on Wed Dec 14, 2011 3:09 pm

neijia_boxer: There is a book called exactly that, man ;)
http://www.amazon.com/Tao-Physics-Explo ... 1570625190
Image
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby Bhassler on Wed Dec 14, 2011 3:12 pm

Achieving mathematical accuracy is neither reasonable nor particularly useful in this context, in my experience it's just nice to have enough of a foundation to do a reality check on theories that are developed through one's own practice.
What I'm after isn't flexible bodies, but flexible brains.
--Moshe Feldenkrais
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby Snork on Wed Dec 14, 2011 3:12 pm

I'm sorry, I should have written that better... I was really responding to what cdobe said and I ended up answering my own question (and I meant geometry as a general term for a space with a relationship between vectors). Looking forward to hearing more
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby nianfong on Wed Dec 14, 2011 3:18 pm

Forces must exist, yes, but we define them mathematically as vectors. And they conform very well to that model. They go in a perfectly straight line for a certain magnitude at a given point in time. The magnitude of any force can only really be quantified mathematically. Can you look at someone pushing a car and just say "he's exerting 356.7 newtons of force on that car"? no. You have to measure how far he goes, in how much time, graph it out, and then take the derivative of the derivative. Or, you have to put a force gauge between him and the car, and guess what? that gauge will have a number on it which would be meaningless without the mathematical construct defining Force as a vector.

You are talking about physical concepts in the world, which we would not have a term for, if it were not for the "mathematical constructs" we are talking about. These concepts are BY DEFINITION, mathematical constructs.

Are you disputing that displacement is a real vector in the real world?
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby cdobe on Wed Dec 14, 2011 3:19 pm

nianfong wrote:There is a book called exactly that, man ;)


It's called "I am right and you are Fong - Applied linguistic hygiene in the natural sciences" :P
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby Bhassler on Wed Dec 14, 2011 3:23 pm

cdobe wrote:With all due respect Fong, but you are wrong here. Vectors are abstract mathematical objects only. Forces exist in the real world. I don't think that's debatable, unless you advocate some whack idealistic philosophy.
I'm more than willing to put my statement under scrutiny...


In the context of communicating an idea in a non-technical, non-academic forum such as this, if vectors are easier to grasp for the general readership, what's the benefit of using the technically correct term over the intuitively understandable one? (Aside from the fact that misuse of the term happens to annoy you and possibly some others as well?) Forces (which exist in the real world) are understood with a different part of the brain than that which understands vectors (the languaging or abstraction of a force). Since the forum relies on words and not feeling, it makes sense to me to use the form of representation which is most in line with what's essentially a bunch of abstracted goo to begin with-- however, I'm open to having my mind changed on that.

Fong: maybe you otter decide whether you want to just arbitrate the definitions of things or if we want to hash it all out in the thread and then maybe clean it up and repost/re-sticky what's relevant later...
What I'm after isn't flexible bodies, but flexible brains.
--Moshe Feldenkrais
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby nianfong on Wed Dec 14, 2011 3:30 pm

Well I want to put it here as reference for anyone. people can refer to it in their own posts etc, and if there are misunderstandings in threads, people can point them here. I can add more terms into the glossary as time goes by if there are more misunderstandings of them.

If people start talking about forces, momentum, and energy interchangeably, it gets very confusing to everyone, and especially confusing to someone who actually understands what the differences between those three concepts are.

-Fong
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby nianfong on Wed Dec 14, 2011 3:45 pm

cdobe, if you don't believe me, perhaps you'll believe wikipedia's various articles on these same physics terms?
from: http://en.wikipedia.org/wiki/Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant direction, typically constrains the object to motion in a straight path. A car moving at a constant 20 kilometers per hour in a circular path does not have a constant velocity. The rate of change in velocity is acceleration. Velocity is a vector physical quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is speed, a quantity that is measured in metres per second (m/s or ms−1) when using the SI (metric) system.

http://en.wikipedia.org/wiki/Vector_(geometry)
http://en.wikipedia.org/wiki/Physical_quantity
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby cdobe on Wed Dec 14, 2011 3:57 pm

nianfong wrote:Forces must exist, yes, but we define them mathematically as vectors. And they conform very well to that model. They go in a perfectly straight line for a certain magnitude at a given point in time. The magnitude of any force can only really be quantified mathematically. Can you look at someone pushing a car and just say "he's exerting 356.7 newtons of force on that car"? no. You have to measure how far he goes, in how much time, graph it out, and then take the derivative of the derivative. Or, you have to put a force gauge between him and the car, and guess what? that gauge will have a number on it which would be meaningless without the mathematical construct defining Force as a vector.

You are talking about physical concepts in the world, which we would not have a term for, if it were not for the "mathematical constructs" we are talking about. These concepts are BY DEFINITION, mathematical constructs.

Are you disputing that displacement is a real vector in the real world?

Forces are not defined as vectors. We use the mathematical concept of vectors to describe them and calculate. There is a big difference here. I am disputing that anything in the real world is a vector. I am however not disputing, that many phenomena in the real world can be mathematically represented as vectors.

Bhassler wrote:
cdobe wrote:With all due respect Fong, but you are wrong here. Vectors are abstract mathematical objects only. Forces exist in the real world. I don't think that's debatable, unless you advocate some whack idealistic philosophy.
I'm more than willing to put my statement under scrutiny...


In the context of communicating an idea in a non-technical, non-academic forum such as this, if vectors are easier to grasp for the general readership, what's the benefit of using the technically correct term over the intuitively understandable one? (Aside from the fact that misuse of the term happens to annoy you and possibly some others as well?) Forces (which exist in the real world) are understood with a different part of the brain than that which understands vectors (the languaging or abstraction of a force). Since the forum relies on words and not feeling, it makes sense to me to use the form of representation which is most in line with what's essentially a bunch of abstracted goo to begin with-- however, I'm open to having my mind changed on that.

Fong: maybe you otter decide whether you want to just arbitrate the definitions of things or if we want to hash it all out in the thread and then maybe clean it up and repost/re-sticky what's relevant later...

Brian, that is a very good point. I do not expect the discussions on this board to become more academic. The opposite is true. For example, I liked Conn's recent descriptions about a certain kind of force generation a lot and could not understand the criticism about it at all. My point is, that the common misconception of what vectors are, does more harm than good. I am under the impression that a lot of people think, that forces somehow travel on the line of the little arrows, that graphically represent vectors. That is not true. The length of the line represents the magnitude of the force. It's more like the height of a bar diagram for example.
Unless we want to do some real mathematics, we don't need the term vector at all. It is totally sufficient to talk about force or its components. In the way the term is mostly used on this forum, we would need to find different terms like lines, chains or paths of force.
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby cdobe on Wed Dec 14, 2011 4:08 pm

nianfong wrote:cdobe, if you don't believe me, perhaps you'll believe wikipedia's various articles on these same physics terms?
from: http://en.wikipedia.org/wiki/Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant direction, typically constrains the object to motion in a straight path. A car moving at a constant 20 kilometers per hour in a circular path does not have a constant velocity. The rate of change in velocity is acceleration. Velocity is a vector physical quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is speed, a quantity that is measured in metres per second (m/s or ms−1) when using the SI (metric) system.

http://en.wikipedia.org/wiki/Vector_(geometry)
http://en.wikipedia.org/wiki/Physical_quantity


Hi Fong,
I do not take Wikipedia as the final word on anything ;) I think the article is a little imprecise in the way it is phrased. And that is my whole point. I am not disputing the underlying physics, but the confusion of natural and mathematical objects.

I am sorry for my booktitle, which was inspired by "All night Fong" :D I thought your comment was a response to me. If you don't like it, please delete the post.
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby nianfong on Wed Dec 14, 2011 4:11 pm

cdobe,
Forces in the linguistic sense are not defined as vectors. "forces of nature" or "economic forces" are insubstantial concepts. But when we talk about physical forces in the real world, they are indeed defined by vectors.

from merriam webster:
1force noun \ˈfȯrs\
Definition of FORCE
1a (1) : strength or energy exerted or brought to bear : cause of motion or change : active power <the forces of nature> <the motivating force in her life> (2) capitalized —used with a number to indicate the strength of the wind according to the Beaufort scale <a Force 10 hurricane>
b : moral or mental strength
c : capacity to persuade or convince <the force of the argument>
2a : military strength
b (1) : a body (as of troops or ships) assigned to a military purpose (2) plural : the whole military strength (as of a nation)
c : a body of persons or things available for a particular end <a labor force> <the missile force>
d : an individual or group having the power of effective action <join forces to prevent violence> <a force in politics>
e often capitalized : police force —usually used with the
3: violence, compulsion, or constraint exerted upon or against a person or thing
4a : an agency or influence that if applied to a free body results chiefly in an acceleration of the body and sometimes in elastic deformation and other effects
b : any of the natural influences (as electromagnetism, gravity, the strong force, and the weak force) that exist especially between particles and determine the structure of the universe
5: the quality of conveying impressions intensely in writing or speech <stated the objectives with force>


Definitions 1 and 4 are the primary ones we are discussing right now. 1 describes anything that actively moves another thing. That's a pretty broad definition of Force. 4 is the vector quantity we are discussing, by definition. If you understand what 4 means, then that actually very accurately frames definition 1. You have to define what it means to move something else, and that would be a change in momentum.

http://en.wikipedia.org/wiki/Force
From wikipedia:
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate, or which can cause a flexible object to deform. Force can also be described by intuitive concepts such as a push or pull. A force has both magnitude and direction, making it a vector quantity. Newton's second law, F=ma, was originally formulated in slightly different, but equivalent terms: the original version states that the net force acting upon an object is equal to the rate at which its momentum changes.[1]


Now do you understand?

For our discussions, we do not need rigorous mathematical vectors, but we do need to understand that every force, displacement, velocity, momentum, all have a direction to them. Energy has no direction, but has an associated momentum when it manifests as kinetic energy.
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby KEND on Wed Dec 14, 2011 4:19 pm

Keep up the good work. As one who has in the past recommended using more scientific descriptions of martial phenomena and introduced[I believe] the first use of Cartesian coordinates to represent five element strike force vectors in my book in '02 I think this is a step in the right direction. The laws of conservation of energy still apply to a punch where is a transfer of energy from muscular contraction and body movement, if the punch is controlled, ie by the arm muscles and the brain[punching through or at a surface point and possibly controlling speed] an additional level of complexity is involved. The objective is to understand better the mechanics and possibly improve on the previous empirically derived methods. Lets not split hairs on definitions, if the sense of what is happening is got across then that is a step forward, just as long as you dont start using 'quantum'[the latest new age fad]
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby nianfong on Wed Dec 14, 2011 4:19 pm

cdobe, really the crux of my argument is this:
do you dispute that displacement is a real, and measurable vector in the real world?
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby bailewen on Wed Dec 14, 2011 4:21 pm

We should ask Brooke about these questions! :D
Click here for my Baji Leitai clip.
www.xiangwuhui.com

p.s. the name is pronounced "buy le when"
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