Quick and Dirty Physics Primer

Before I can dive into the martial arts and how the science applies, I need to at least introduce some concepts from physics.  If any of this sounds completely confusing to you, then you may want to find an alternate source to get a deeper explanation.  I recommend khanacademy.com.  The following text is a bit dry for the typical martial artist.  So, you can skip it if you want, but you may need to come back to understand later articles.

Displacement, Velocity, and Acceleration

Displacement(which is like distance and will be treated as such in most situations here) is one of the fundamental concepts in physics.  Space exists.  Displacement is the measure of how far apart two points in space are.  For example, “that punch missed me by 3 inches”.  Here, “3” would be the measure and “inches” would be the unit of measure.

What happens when we put timein the mix?  When we go a distance over a period of time?  Then we get velocity (which is like speed and will also be treated as such in mostsituations here).  For example, if a person runs 100 meters (m) in 12 seconds (s), then their (average) velocity is 100m/12s = 8.33 m/s.  In general, the units for velocity are distance divided by time (distance/time).

Most people are familiar with the standard of testing an automobile’s “0 to 60” time, which means “the amount of time it takes a car to go from 0 mph to 60 mph”.  Just like velocity was a difference in displacementdivided by time, acceleration is a difference of velocity divided by time.  So, a car that goes from 0 mph to 60 mph (note that ‘mph’ means miles/hour, which is distance divided by time) in 5.2 seconds has an acceleration of (60mph – 0mph)/5.2s = (26.8224m/s – 0m/s)/5.2s = 5.16m/s2 = 11.54mph/s.  The whole “seconds squared” unit is sometimes hard for people to grasp.  So it helps to think of it this way: the car can increase its speed by 5.16 m/s per second.

For those of you who know calculus, acceleration is the derivative of velocity, which is the derivative of displacement (all with respect to time).


No, I’m not talking about Star Wars or “force fields” (well technically…oh nevermind).  I’m talking about physical forces.  Gravity is a force.  Atoms are held together by various forces.  Pushing someone involves applying a force.  This is something that is highly applicable to fighting.

According to Sir Isaac Newton, force (commonly depicted with the capital letter ‘F’) is equal to mass times acceleration, or more succinctly: F = ma.  Much like distance, mass is another fundamental measure of the physical universe.  It specifically measures the amount of matter an object has.  Note that this is different from “weight”, which can change depending on the force of gravity (like on the moon).  I also want to highlight the importance of this concept by pointing out that the formula, F = ma, is the second of Newton’s three laws of motion (the first being inertia and the third being that every action has an equal but opposite reaction).


Early, I said that displacement was like distance and velocity was like speed.  Vectors are what make them different.  Distance and speed are known as “scalars”.  They are represented only by a single quantity (5 meters, 55 miles per hour, etc).  Vectors, however, are represented by two quantities: magnitude and direction.  So, 5 meters might become 5 meters to the left.  55 miles per hour might become 55 miles per hour North.

Understanding the concept of vectors is extremely important for fighting.  As you may have guessed, forces are vectors.  We don’t just push people.  We push them in a direction.


I realize that all of that text was really light on the fighting and martial arts, but just like studying any subject, you need to understand the vocabulary and base concepts before you can absorb any of the really good stuff.  The next post will be juicier.  I promise!


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