oragami_itto wrote:Rotation is just a principle of the lever
Sigh.
The scientific principle is leverage or mechanical advantage. A prerequisite for leverage is a lever arm (distance) and a fulcrum (axis/pivot point) about which the lever arm can rotate.
Rotation is not a principle and is not limited to the action found in a lever.
There are three classes of lever. The first and third classes can increase one's effort or decrease one's effort (mechanical advantage greater than 1 or less than 1, respectively). Only the second class always has a mechanical advantage of 1 or more.
https://en.wikipedia.org/wiki/LeverOne of the ways of trapping, leading to unbalancing an opponent, is to have/put the opponent's body in a position where his mechanical advantage is less than 1. For example, try to push someone so that when you make contact push with your hand just in front of your chest or shoulder, your arm bent well beyond 90 degrees. You'll have a difficult time extending your arm due to your poor mechanical advantage. (Timing to meet your opponent's push/strike so that his arm is in a position that is poor for him is one way to have an opponent push himself away from you.)