Physics of Karate – No Woo Required
Posted by mattusmaximus on November 14, 2009
I’ve practiced martial arts of various styles for 20 years, and in all that time I’ve heard a number of very strange & woo-filled explanations for why people can accomplish the physical feats they can. One such example is breaking wooden boards with the bare hands & feet – often people provide an explanation by referencing so-called “chi, ki, or qigong energy”. The whole concept of chi is more of a philosophical concept than anything else, and it is little more than a “dragon-in-the-garage” (an untestable notion that cannot be verified through scientific means).
Well, I’m here to tell you that such physical feats as board breaking can be performed & explained simply by referencing the known laws of physics – no woo required. Take a look at the video of me performing such a break with five pine boards at once…
How do I accomplish this feat? Here’s how: I hit the boards really hard – the question is how do I generate such a large force of impact? Read on…
1. Materials: First off, there’s a good reason why I’m hitting pine boards – they are a soft wood. Whenever I’ve seen martial artists doing breaks such as these, they hit either pine boards or a brittle material like clay bricks or concrete slabs. In addition, when striking wooden boards, successful strikes always go with the grain of the wood because the wood is structurally weaker in that orientation. So, in a real sense, karate practitioners are kind of cheating by using these materials – if you really wanted to see something impressive & “supernatural”, perhaps someone could display slicing through a steel I-beam with the edge of their hand. I think there’s a pretty good reason why we never see a “chi-master” doing that! 😉
2. Spacers: Notice the spacers that I’ve got placed in between the boards. This is another common trick that is used whenever board breaking is performed. By separating the boards like this, I really only have to break one at a time as opposed to one large, massive chunk. In more technical terms, the momentum of my strike is slightly reduced by breaking only the top board, which allows the remainder of my hand’s momentum to continue to the next board, and the next after that and so on. This works for the same reason why train cars are slightly decoupled from one another – once the engine gets moving, its momentum helps to move the next car when the coupling catches, and their combined momentum help to get the third car moving when its coupling catches, and so on.
3. Impulse-Momentum Theorem: the rest of it has to do with the physics of impulse & momentum. In equation form, this theorem (which is another way of expressing Newton’s 2nd Law) can be written as follows:
F Δt = m Δv
F = m Δv / Δt
where F is the force of impact, Δt is the time of impact, m is the mass behind the strike, and Δv is the change in velocity of striking hand (or foot). In order to break the boards, one must maximize the force of impact, which can be done in a variety of ways…
*Maximize the mass: instead of merely hitting the boards with my fist, I turn & twist my entire body into the strike. By doing so the mass (m) is greatly increased, and so too is the force.
*Minimize the impact time: the boards are placed onto solid supports (in this case the stools) which do not give under the impact. Because the supports are not excessively elastic or bouncy, the time of impact is reduced to a minimum, which has the effect of greatly increasing the force of impact.
*Maximize the velocity: by dropping my body mass so dramatically, I convert a large amount of gravitational potential energy into kinetic energy. And since kinetic energy is proportional to the square of the velocity of an object, by doing so I provide a great deal of velocity (and therefore momentum) which can carry all the way through all five boards as previously mentioned.
So there you have it, folks – a thorough explanation of how such board breaking feats are done, without a mention of chi/ki/qigong or any other supernatural woo-woo. This is a very good example of applying Occam’s Razor, and I thoroughly enjoy sharing this lesson with my students.
Sadly, there are those who would rather deny scientific reality & the laws of nature in favor of the delusion that they have some kind of mystical power over “chi energy” and can therefore do physically impossible things. And even more sadly, these delusions can lead some people into serious injury. Here are two examples of what I’m talking about…
*The first is of one of these so-called “chi-masters” who believes that he can throw people merely by “projecting his energy” at them, but – interestingly – he only seems to be able to perform these “throws” on his true-believing students. What happens when he encounters someone who isn’t a true-believer in his abilities? Take a look at this video to find out:
There is an entire group, almost cultish in nature, called Yellow Bamboo that purports to teach people how to “focus & project their chi” with equal levels of failure. Just search Youtube and you’ll find plenty of videos of the Yellow Bamboo woo-meisters getting pwned.
*But if that isn’t bad enough, here’s a whole other level of fail… this next clown is so far down the “chi-master” rabbit-hole that he actually believes that by “focusing his chi energy” he can make himself impervious to blades. And to prove it, he hacks into his own arm with a razor-sharp machete! How do you think it went? (Warning: not for the squeamish)
Folks, in my opinion, it just doesn’t get much more stupid than that. The moral of the story is simple: when it’s you and your beliefs vs. the laws of physics, physics always wins.