Actually, the equation for force involves more than just mass and acceleration. The full equation is F=ma+cv+kx. This longer equation takes other variables into consideration, such as wind resistance, gravity, friction within joints, muscle tension, and energy lost through heat. This longer equation for force contains 6 parts: (mass x acceleration) + (velocity x displacement) + (damping x stiffness)
- Mass. Mass is basically the fist's weight.
- Acceleration. Acceleration is how quickly the fist increases in velocity.
- Velocity. Velocity is how fast the fist is moving.
- Displacement. Displacement is how far the fist moves.
- Damping. Damping accounts for force that is dissipated by flexible surfaces and structures contacting each other. Damping occurs when there is weakening in the structure of the punch. When the fist impacts the chin, it cause the skin, muscles, and joint to collapse somewhat, which dampens, or reduces, the force of the punch. If the fist is covered in boxing glove, the striking force is reduced by dampening effect of the glove's padding. Some damping also occurs when the body oscillates. Since the body is mostly water, it oscillates when shaken by the reaction to the action of the punch. Damping is also caused by friction. Muscles generate heat by the friction of rubbing against each other, which uses up energy. Energy is also wasted by other types of friction, such as the arm rubbing against the body during a punch.
- Stiffness. Stiffness is how rigid the fist and arm are at impact. The stiffer the fist and arm are on impact, the greater the striking force. The hardness of the striking surface increases the force delivered because reaction force will not be absorbed, thus, the knuckles of the hand strike harder than the knife hand.