# Types of force

Force is any influence that causes an object to undergo a certain change related its movement, direction, or geometrical construction. A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate, or a flexible object to deform, or both. Force can also be described by intuitive concepts such as a push or a pull. A force has both magnitude and direction, making it avector quantity.

The following are some types of force:

## Muscular force

Muscles operate by contraction, so when a muscle pulls a body part in one direction, for the part to return to its original position, another muscle must pull it back. No one muscle in the body may generate the force required to deliver an effective blow. All the muscles of the body must act in concert to generate the required force.

## Gravity

All objects exert an attraction on all other objects. The force of that attraction is proportional to the mass of the object that attracts. The attractive force of the earth is called gravity. Since gravity always exists and it is predictable, it is useful in combat. You may not be able to move a larger opponent horizontally and you certainly may not move the opponent vertically, but you may use gravity to cause the opponent to fall by causing the opponent to lose balance. This may be accomplished by pushing when the opponent pulls or vice versa.

## Friction

Friction is the resistance a body exerts upon another while moving over it. The friction between two surfaces:

• Is proportional to the force pressing them together. The heavier you are, the more difficult it is for you to slip when punching.
• Depends upon the nature of their contact surfaces. You are less likely to slip with rubber soled shoes than with leather soles.
• Is independent of the area of the contact surfaces. Contrary to popular belief, there is no change in friction whether you are resisting a force while standing on one foot or on both feet. One skidding tire will stop a car just as fast as four skidding tires (as long as the heat generated at the point of contact remains constant, which is nearly impossible.

## Momentum

Momentum (force) is produced by an object in motion. Force is equal to the product of mass of the body and its acceleration (f=mv). In a punch, the mass of the fist may not change, but the velocity of the fist is variable. If the fist constantly accelerates over the distance to the target, the final velocity will increase the striking force of the punch. The longer a force acts on an object, the greater the final velocity, so you should maintain acceleration until contact is made, do not snap back before contact. Muscles work in sequence to produce maximum power; you should start contracting each succeeding muscle the point of greatest velocity from the previous muscle. All muscle forces must be applied toward movement in one direction. The following three items describe how momentum/force is induced in an opponent.

## Impulse

Stopping force is proportional to the product of the mass and velocity of the object in motion and is inversely proportional to the time required to stop the object. When this is applied to the force equation, the result is: stopping force x time = mass x velocity (ft=mv). Therefore, if the mass and velocity of a punch is constant, then a small stopping force will require more time to stop the punch and a large stopping force will require less time. The product of the time and the force required to stop the punch is called impulse.

If the time required to stop an advancing object is near zero, then the force required to stop it will nearly equal the momentum of the object. When an object is stopped in an extremely short time, the product of the force and time is called impulsive force. This occurs when a punch strikes the body or a bat strikes a ball.

## To transfer of maximum force to an opponent

To transfer maximum force to an opponent, you must induce momentum in the opponent in the shortest time possible, apply all your mass into the strike, and achieve maximum velocity with the strike. This means a maximum power punch will have the weight of the body behind it, have all the muscles in the body working to accelerate it maximum velocity, and will induce momentum in the opponent in minimum time.