arnisador said:
The pseudo-scientific descriptions of the techniques are typical of what one hears from those who believe that what they are doing is scientific despite their lack of training in the subject:
"Some important physical quantities related to striking are momentum (p = mv), and kinetic energy (KE = 1/2 mv^2). The physics equations describing these quantities depend on mass and velocity, not on the amount of distance traveled in executing the strike. In this demonstration, the utilization of proper principles regarding speed and body alignment, not travel, gives tremendous power to the strike."
I'll agree that the last sentence is perhaps a misapplication of the physics equations in question. However, when taken separately, both the descriptions of the physics involved
and the description of the physical technique are accurate. Furthermore, to my knowledge, the AKKI has never claimed to be "scientific" in any way. They
do claim to take a logical and rational approach to self-defense and motion; this is subjective, to be sure, as is the entire realm of martial arts.
arnisador said:
Focusing on amount of distance omits the fact that velocity is exactly rate of change of distance (displacement), i.e. p=mdx/dt, but leaving that aside, as well as the fact that p depends on velocity but K.E. depends on speed, if we assume that the strike is initially started from a previously stationary hand (null velocity, null acceleration), then to get more speed one needs more distance through which to accelerate. For a given velocity it's all well and good to say that p=mv, but to get a reasonable speed requires traveling through a certain distance. It seems to me that the real question here is how rapidly can one accelerate through the distance from the weapon to its target, that is, p=m*int(a(t)) is likely the best way to analyze it. Under the reasonable simplifying assumption of constant acceleration and null initial conditions, v=at and d=at^2/2 so the quantities are essentially interchangeable. After a given distance, you have a certain speed, and a certain speed corresponds to a given distance (until speed reaches a maximum or starts to decrease, if it does). Of course, until you can argue whether or not the collision is inelastic and how much energy is transferred to internal energy rather than energy of motion, it doesn't mean much.
We both agree that v=dx/dt. (In any case, whether we agree or not, this is a mathematical fact. :ultracool ) However, when you begin speaking about
acceleration, you're changing the nature of the argument. The AKKI statement did not address the acceleration of the striking hand. It should have, in my opinion, but that's moot.
Muscular contraction cannot be adequately described using the physics model of kinematics. There
is a small component of acceleration at the beginning of a contraction. However, this acceleration takes place during the initial
micro- or
nanoseconds of the muscle action. The rate of muscular velocity is entirely dependent upon a person's genetics, muscular phenotype, and level of muscular training. I suppose we could discuss neuromuscular physiology, muscle fiber biochemistry, and motor unit recruitment, but that would be far beyond the scope of this thread (probably the entire forum). In any case, maximum velocity is achieved at the very
initiation of muscular contraction. Once full contraction/movement begins, no further velocity is achieved or possible. This is why it is possible to strike with maximum velocity while moving very short distances.
You're right about the nature of the collision. I don't think physics can accurately describe the nature of flesh on flesh impact. There are probably far too many variables at play. As I said earlier, almost the entire realm of martial arts is subjective.
arnisador said:
"Using these principles, even the small mass of a finger whip has enormous destructive power. This is the same principle that allows the tip of a bullwhip to be accelerated so that the speed of the tip exceeds the speed of sound."
The
crack of a whip comes from the whip forming a circular loop. Apparently this person can twist his forearm into a full circle.
This is just more pseudo-science used to trick the unwary. It's no different than claiming that you're moving people with your ki, to my way of thinking. It's a sales gimmick that is meant to impress people who don't know better than to believe it.
I doubt the person who wrote the AKKI statement was even aware of this particular description of whip physics. I believe the analogy is making reference to the notion of progressive acceleration (each successive part of the chain accelerates independently, thereby increasing the total acceleration exponentially). From what I understood of the abstract you linked and your subsequent discussion, the analogy is still appropriate. While the "loop" may not be present, progressive acceleration is.
Once again, I wouldn't call this "pseudo-science." It may be a misapplication of scientific principles; at the least it's an attempt to logically apply those principles to describe human movement. From my personal experience, these analogies have only been used to spark thought and understanding. That's a far cry from attempts to "trick the unwary." I agree that the existence of many people with those ulterior motives justifies a skeptical approach, but
assuming those motives exist is far from objective. It depends on one's perspective, I guess.
MH
