Force generation in Tai Chi is a function of the use of biomechanics consistent with the laws of physics. The core basis for force generation is the conversion of potential to kinetic energy and vice versa.
How to convert potential energy to kinetic energy in a recurring manner, a constant process of store and release is a topic that is studied physically when you practice the 22-form.
Various mechanisms strewn throughout the form whether in the form of an actual physical motion or mental imagery is to train the use of intent in tandem with biomechanical actions to generate force.
An example of this would be the palm strike at the end of Brush Knee, Twist Step whereby :-
a) Physical motion – the body moves towards the arm to initiate the potential energy storing motion. Then the hand comes out to strike. This is powered by kinetic energy which has been converted from the stored up potential energy.
b) Mental motion – since we move at a slow pace when practicing Tai Chi this makes it difficult to initiate a sudden shock force through the physical palm strike as this requires the ability to suddenly accelerate the arm and perform the strike like a whip.
Why we avoid doing this is because to do so would be turning this into a fast form practice. We would also be missing out on other ways of training such as the use of imagery to optimize the speed for moving the striking hand from Point A to Point B.
3. ENERGETIC FORCES
In GM Wei’s Yang style Tai Chi we study six fundamental energetic forces (掤, 按, 擠, 采, 列, 捋) that is augmented by additional two forces (肘, 靠) for a total of eight energetic forces. These forces can be represented by mental spherical lines outside the body that tracing the path of the particular force in space between the point of origin of the force and the convergent point that the energetic forces are targeted at. Yes, you read this correctly – forces. Not force. Forces.
We normally read of how Peng Jing is used to fajin. When we do fajin we use not just Peng Jin but An Jin and Ji Jin together; at the same time (we call this Jin grouping as Peng An Ji (掤按擠); the other grouping being Cai Lie Lu (采列捋)). The term for this mixing of energetic forces is Blending Energy Method (混合勁法).
We use a trio of forces instead of a singular force because this makes it more difficult for the opponent to counteract your force when they are coming from three different directions simultaneously. When you add in the augmented forces you can have a total of four or five forces directed at one at the opponent.