Another example of how physics applies to karate is in take-downs. This is when you use your opponent's bodyweight against them (which I know is more Judo inspired than actual karate, so just bear with me). But what I observed is with minimal brute force a person with little mass can take down an opponent with much bigger mass. This is done with speed. And as the formula for force goes, it is equal to the mass of the fist times the acceleration of the acceleration of the punch. So, short people of the world don't worry, with enough speed you can beat a much bigger opponent.