Lara Chanthongthip Labor 2: Flying Circus of Physics: Karate by Lara Chanthongthip is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.
Karate is an ancient martial art originating on the island of Okinawa. It is a combination of two fighting techniques. One technique was from Okinawa called te, and the other technique called kenpo was from ancient China. Karate is a defensive striking art that uses punching, kicking, knee and elbow strikes, and open-hand techniques. In this paper, I will discuss the physics of striking an object and the importance of proper body positioning.
In order to break an object, the striker must hit the object as hard as possible. To do this, one must move their weapon as fast as possible. For the purpose of this paper, the object being struck is a board and the weapon striking the board is the hand of someone highly trained in Karate. To understand the physics behind a hard strike in karate, Jon Chananie says in “The Physics of Karate Strikes,” that force and momentum is a possible explanation.
WARNING: Do Not Try This At Home! or the following may happen (see video Karate 1 and then video Karate 2)
A hard strike explained in terms of force and momentum addresses conservation of momentum. Newton’s third law states that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first along the same line of interaction. Chananie defines in his paper: force (F) is acceleration (a) times mass (m), momentum (p) is mass times velocity (v), and since acceleration is the change in velocity over time (t) it is the derivative of velocity (v) with respect to time. Thus, the change in momentum is equal to force times time: ∆p=Ft. Momentum is a conserved quantity since it can neither be created nor destroyed. The conservation of momentum states that momentum can be transferred between objects, but the total can never change. Momentum is transferred between objects and in the case of this paper it is transferred from the hand to the board. Since momentum can never change, force and time are inversely proportional. This means that one can deliver a given amount of momentum by transferring a lot of force for a small amount of time or by transferring little amounts of force for a longer amount of time (Chananie 1). To deliver a hard strike, one must have a lot of momentum delivered in a short amount of time to have the greatest force: F=∆p/∆t. The sudden transfer of a lot of momentum from the hand to the board causes the board to break.
The importance of proper body positioning is crucial for maximizing the effectiveness of karate techniques. Sensei Peter Lindsay says, “Your stance is the platform upon which everything else is built.” He says a low stance creates a lower center of gravity which will promote good stability and foster strong muscular development (Lindsay: Stance). To define center of gravity, Jacques Chaurette says it is the point at which if the body were suspended it would be perfectly balanced in all positions. The center of gravity can change on a human if they lower their body closer to the ground (by assuming a lower stance). This will cause more mass to be closer to the ground thus becoming more stable. The forces that the body is subjected to during a punch or a kick are related to the center of gravity (Chaurette).
Click Here for Chaurette's article to better understand the center of gravity.
Chananie, Jon. “The Physics of Karate Strikes.” Journal of How Things Work. 1.Fall 1999: 1-4. Electronic.
Jon Chananie’s article was about the force and momentum of striking an object related to karate. I really liked this article because it was very easy to understand and I found a lot of useful information. This was a credible source as it came from a journal.
Chaurette, Jacques. “Karate and the Center of Gravity."
Jacques Chaurette’s pdf was about understanding the center of gravity (CG) and how a lower CG can help the stability. This was a good site because he had lots of images to help with understanding the concept and also an activity involving shapes and finding their CG. Chaurette seems to be a credible source because of the ability to demonstrate his knowledge through images.
Lindsay, Sensei Peter. “The Four Cornerstones.” Pawnee Shotokan: martial articles
The Pawnee Shotokan site was about the four cornerstones of Karate which Sensei Peter Lindsay wrote about. This was a good source because it gave me a quote to which I could expand my knowledge of why proper body position was good for stability. Sensei Lindsey is a credible source because he is very knowledgeable about karate.
Lara Chanthongthip Labor 2: Flying Circus of Physics: Karate by Lara Chanthongthip is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.