Mechanics and physics

Hello Rabbi
A question for a physics doctor. In a punch, there is a calculation of the force as half of the mass multiplied by the speed. What I don't understand is what is the explanation of the force of repulsion, i.e. how does it work? And secondly, how is this type of force expressed in a punch? Is it just the above calculation of force or also some other energy (for example, the nervous system that determines speed, what else does it determine, and how does it work?)