Bio-mechanics & Centripetal / centrifugal force

[GaryR]

“The chin [intrinsic strength] should be
rooted in the feet,
generated from the legs,
controlled by the waist, and
manifested through the fingers.” --Attributed to Chang San-feng (est. 1279 -1386


Note: Due to the nature of the material--diagrams and math equations, my post will not paste directly- So click below to access (thanks to XinKuzi for hosting)

-- http://yinqianhe.com/rsf/postcentrip.pdf
-- http://yinqianhe.com/rsf/postcentrip.doc

I have included a PDF- which preserved all of the pictures, and a word document so people can cut/past if they like for discussion.

Questions to keep in mind for this thread; please help this be productive and stay on topic

1) In reference to the material posted (from a mix of sources)---What role does centrifugal/centripetal force play in your practice? Describe as specifically you can, explain, or demonstrate please
2) Same Q as above for---Nonuniform circular motion
3) Same Q as above for--BASICS OF BIO-MECHANICS
4) Same Q for Energy & momentum.
5) Can you identify/understand the Nexus between bio-mechanics, energy, momentum, against the Centrifugal and centripetal force?

Note; this post / info for discussion can and should range from highly technical--calculus for ex, (everything boils down to math anyhow), to practical implications and springboards for many models and ideas.

I also barely touched on the topic of Centrifugal force, but I ran out of time. More on this from me later, when I get time, and video as well.

Please take the time to click the link, read, and contribute! TONS of material to discuss, and TONS of practical things can come out of it.

 

[GaryR]

This is sort of a piggyback on the previous thread re centripetal force, etc. But with video so as to discuss perhaps something in more specific and narrow terms, the last post was a bit robust to begin a practical discussion I realize.

The video depicts a few simple examples of such forces at play. Unfortunately the audio setting was F-ed up (I was filming a lesson for an out of state visitor), so you can't hear my diatribe the whole time while demonstrating, probably for the better.

The very basic idea is to of course push against the ground for momentum, turn the waist / body and swing the arms.
The resulting method / technique are essentially inconsequential at this point, but it should be fairly obvious what can come from it. The movements are exaggerated to start, and more disconnected. Here the student is a prior Wing C. guy, so I'm trying to get him to relax; he also wanted things beyond the scope of his skill level on tape since he is out of state.

More caveats; Yes I know I am not perfect. My posture is a bit off (just finished a J.D., have been hunched over a computer all day for months), plus I’m battling retrolystisis (spelling?) of L5, so my back is a bit off, but I'm still moving decently considering.

Anyway, the centripetal force begins from pushing from the ground and turning the toe/knee/waist closed, while opening the opposing side using centrifugal force (my right hand in clip), as the other hand uses centripetal. Another caveat; I do not have any degree or any official academic background in physics, neurophysiology, kinesiology, etc. (my background is Avionics / IT and Law), so hopefully someone who knows more about the exact process will chime in to assist if the question/need arises and / or I get something wrong e.g. Centripetal force.

The two man portion of the clip was my first attempt at showing that student how to "soft spar" sort of a hybrid between push hands and sparring, I’m sure many of you here do the same. The idea is to keep moving, right, wrong, bad form or not, just keep the motion. It's not a contest, everyone should take turns, give and take, and not everyone you meet will be trained in the arts. Random as@ attacks from many venues should be tried on each other, even if you have to break form / connection and structure. I love working with Boxers, MT, WC guys etc, who like to keep pressure on, how else will you get better? Here, I am trying to get the student to hit me and keep moving, he is reluctant, perhaps my previous demos weren’t so soft...

So, thoughts on the physics and actual principles behind these movements? Comparisons to your own methods or movement? Constructive criticism is of course welcome (even better if you have a clip replicating and demonstrating what I do / don't do correctly from your view-- but I can probably point out how I suck in this clip just about as well as anyone...we all have stuff to work on.


http://www.flowingcombat.net/drill11.mov.3gp

 

[Buka]

Rather a complicated explanation, no?

When do I get to hit someone?

 

[ACJ]

One of the problems with looking at circular momentum and acceleration in relation to body mechanics is the idea of force moving on a simplified mass (a single point) and although you have discussed body parts moving independently of each other. When discussing the circular movement, the direction and location of the generation of force is quite strange compared to the standard physics model.

As to the questions, the physics are rarely discussed in class, but circular motion underpins nearly every movement we make. It is taught in a way that uses this fact to make the system more cohesive, essentially we teach a number of hip movements and associated foot and knee movements, and from there extend them into a number of other movements (kicks, knees, shoulder charges, punches, headbutts, weapon strikes, throws, footwork, etc.).
I think it interesting that some people differentiate circular and straight movements or even arts. From my perspective, straight line are actually just made up of lots of circles and circular movements are also made of circles.

What particularly annoys me about energy in relation to MA is how I see a lot of people try to us "f=ma" as a description of how much damage they would impart on another body. Thank you, finally someone who is using the kinetic and potential energy. The only time in training we look at energy and momentum (we just hit things and if anyone was to try and explain energy and momentum, i think the reaction would be "duh?" ) is during plyometric training when the conversion of kinetic to elastic potential and back to kinetic is fundamentally integral to the training.

 

[GaryR]

lol, often its better to do first, and have it explained later..