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Analysis of Aikido techniques and practice with the aid of Physics
As far as I know there's only one interesting book that deals with the Physics side of Aikido, 'Ratti, Westbrook':Aikido and the Dynamic Sphere', but it's just a description with nice illustrations; the few other essays I've met spend just a few and usually wrong words, using terms like 'lever' that are not correct. So I'll try to have an exchange that can make our knowledge of Aikido richer and also, I think, stimulating.
I'll start with a few examples:
1- lever
In Aikido there are no levers: when you apply a force to something or somebody (say uke) you have to take into account the overall reaction (a force from the earth passing through uke), so the result is a combination of two forces and an axis (it's called a tensor) whose effect is a rotation.
(To clarify things look at the way we walk: our foot pushes the earth (exerts a force downwards and a little backwards upon the earth) and the earth reacts with an opposite force through our foot, so our foot goes high and forward).
2- work
A force has two elements: intensity and direction, and can be represented by an arrow (usual name a vector); its effect in general is a displacement, which has similar elements, length and direction (still a vector). Work is defined as the product of the force for the component of displacement in the same direction.
It's interesting to underline that in Aikido force and displacement are in general perpendicular, that means that work is null. So Aikido techniques are generally made without effort.
3-energy
This is a term that is often used in creative ways, sometimes meaning force, other times something in other dimensions. In order to avoid misunderstandings we use the simple mechanical definition, that is, the ability to perform work.
This is also interesting for Aikido, since when work is null we have used/created/wasted no energy; so in general Aikido moves don't waste energy.
In a simple move (sa
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