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Physics of a Punch

In understanding the generation of power in strikes in martial arts, it is instructive to study some physics; the science of physics can give you a thorough understanding of how power/force is generated through movement. Therefore, here we will examine how punches can generate maximum power and effectiveness, through physics. We choose punches because it is a common attack in terms of fighting. Of course, these principles can be applied to any strike or kick.

The Formula for Force

The specific formula for force is: F=ma + cv + kx

  • F= Force – Power of the punch
  • m= Mass – Weight of weapon
  • a= Acceleration – How quickly the weapon increases in velocity
  • c = Damping – The weakening of force when two surfaces make contact
  • v= Velocity – How fast the weapon is moving
  • x= Displacement – How far the weapon is moving along a vector
  • k= stiffness – How rigid the weapon is (support)
  • Vector – Line the fist travels along
  • A deviation from the vector will cause a loss of power

By Peter Harrison (originally posted to Flickr as Block and Punch) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

By Peter Harrison (originally posted to Flickr as Block and Punch) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

It should be noted that velocity is displacement – how far the weapon travels – and the time it takes to travel. Acceleration is a change in velocity and the time it takes to achieve final velocity. The force of the fist is its mass and its acceleration. The pressure of the punch is the force of the weapon and the striking area of the weapon – a smaller striking area will have greater pressure. The force of pressure is greater when the surface area of the weapon is smaller because the smaller object is pushed into a smaller area; imagine pushing a thumbtack into a wall; typically it penetrates the wall, something that couldn’t be done with a thumb alone. This can be seen as penetration and is why we kick, for instance, using the ball of the foot or the heel. Of course, you can have greater impact with a bigger weapon, but the penetration won’t be the same. This, also, is where mass, or weight, comes into play; more weight, more impact: A wooden baseball bat is going to hurt more than a plastic bat. Also, this is why you must use body mechanics to create power; turning your body into a punch, dropping your weight into a strike, moving the body forward into a punch, etc.

Distance is how far a weapon travels. Speed is the distance it moves, including if it strays from it’s path (a deviation from the vector), and the time it takes to hit its target.

Notice that damping – weakening of force after impact (see above) – causes a loss of power. This is one reason when a fighter punches and hits an object (a target on the opponent), he or she will re-chamber and hit again along the same path or choose another path or use the other fist, leg, etc. In other words, the process of building up power must start all over again, in some form. Of course, this is also why a block will weaken impact, even if “some” of the punch gets through to its target. Many things could dampen the punch. Being underwater, for instance.

Stiffness (again, see above) is another principle that is revealing to look at: This principle explains why strikes must have support or leverage of some kind to be effective. You must anchor part of the arm to the body to give it support or even use the other hand to support the arm of the striking hand. There are various ways to lend support or leverage, but you get the idea.

By Denis Gustavo [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

By Denis Gustavo [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Noticeably, all of these principles point to time and distance. Basically, the amount of distance a weapon travels, plus the amount of time it takes to travel, determine the power of a punch. Other factors, as mentioned, enter into it; how well supported the strike is by the rest of the body, for instance; what path the strike travels along; the weight of the weapon.

Therefore, angle, path, mass, speed and travel all factor into the power behind your punch.

Featured image: By Shanghai killer whale (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Get the book, Fight Like a Physicist, which is a thorough exploration of how physics applies to martial arts, written by a physicist and martial artist.

 

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