Mehcanical Principals Essay, Research Paper
Assignment
Mechanical Principles and Concepts Related to Movement
Stability
The concept of stability is related to equilibrium, a state of equalized forces on the body. Stability is the ability of the body to regain equilibrium after it s has been displace. There are two types of equilibrium, static and dynamic. Static is where the center of gravity is un a stable position, like in performing a tilt in wrestling or a handstand in gymnastics. Dynamic is where the center of gravity is in motion, like in wrestling when shooting in on the opponent.
Principle
The lower the center of gravity is to the base of the support, the greater the stability will be. In wrestling lowering your body making your stance semi crouched increases stability.
Concepts
1. To achieve greater stability, lower the body over base of support.
Principle
The nearer the center of gravity is to the center of the base of support, the more stable the body. In sprinting, a runner lean forward to shift weight in the direction of motion, or when on a balance beam the arm or leg on the opposite side from which the person is leaning is raised to shift the center of gravity back toward the base support.
Concepts
1. For greater stability, maintain a body position with the center of gravity over the base support.
2. When falling or leaning to one side, raise and lower the arms or legs or some other body part on the side opposite the direction of the fall or lean (distribute weight evenly.)
3. When carrying or lifting a heavy object keep the objects close to the body while bending the knees and keeping back straight.
Principle
The larger or wider the base of support the more stable the body. In wrestling having your feet spread farther apart gives you a wider base and more stable.
Concepts
1. Spread feet to increase the base when standing. The feet should be in the direction of the movement for the added stability.
2. For activities where a stance is required, using both hands and feet will create the widest base.
3. When receiving a fast moving object, or a heavy force, widen the base of support in the direction from which the force is coming.
4. When applying a force, widen the base in the direction the force is to be applied.
Motion
Motion implies movement, which means to destroy or upset the equilibrium of the body. To effect the motion of a body, a force is required. Everything that moves is governed but the laws of motion formulated by Sir Isaac Newton.
Principle
Newton s First Law-A body at rest will stay at rest and a body in motion will stay in motion at eh same speed and in the same direction unless acted upon by an outside force.
Concept
1. Once an object is in motion it takes less force to keep it going at the same speed and in the direction. It is much harder to get a bicycle in motion then it is to maintain the speed once it is moving.
2. The heavier the object and the faster it is moving, the more force it takes to overcome it s moving inertia, or to absorb its momentum.
Principle
Newton s Second Law-The change in velocity of an object its directly proportional to the force producing it and inversely proportional to it s mass.
Concept
1. The heavier the object, the more farce needed to speed it up or slow it down.
2. An increase in speed is proportional to the amount of force that is applied. (> Amount of force = > speed)
3. Momentum is a measure of both speed and mass. If the same amount of force is exert6ed for the same length of time on two bodies of different mass, greater acceleration will be produced in the lighter or less massive object. If the two objects are propelled at the same speed the heavier object will have the greater momentum once inertia is overcome and will exert a greater force than the lighter object on something it contacts.
Principle
Newton s Third Law-For every action there is an equal and opposite reaction.
Concepts
1. Whenever on abject moves, another object moves too and in the opposite direction. When you push something, it pushes back; when you pull something, it pulls back.
Linear and Rotary Motion
Motion is either linear, movement in a straight line and from one point to another, or rotary, movement of a body about a center of rotation, called the axis. The human body usually employs both of them.
Linear
In running the body should be kept on a straight line from start to finish and also the feet and arm movements are in a straight line back and forth, not sideways across the body
Rotary
In most human movements, rotary is turned into linear. It is increases when the radius of rotation is shortened, and decreased when the radius is increased. Tucking the head in when performing tumbles in gymnastics increases the rotation of the body.
Leverage
Efficient body movement is made possible through a system of levers. A lever is a mechanical device used to produce a turning motion about an axis. A lever consists of a fulcrum, force, and a load. The bones of the body work as levers, the joints are fulcrums, and the force is produced by the contraction of muscles.
There are three types of levers. First class, force, fulcrum, load. (May produce speed and strength.) Second class, fulcrum, load, force. (Produce strength) Third class, fulcrum, force, load. (Produce speed) The majority of the human body consists of third class levers; therefore the human body was built for speed.
The length of the force arm is the key to producing speed or strength. Great strength = force arm should be as long as possible. Great speed = force arm should be shortened.
Concepts
1. Levers are used to gain a mechanical advantage by either producing speed or strength.
2. Greater speed is produced but shortening the force arm, and greater strength is produced by lengthening the force arm.
Force
Force is the effect that one body has on another. It is invisible, but is always present when motion occurs. Although force is always present with motion, force can be present without motion. For example, you can exert a force on a wall by pushing on it. The was does not move but you are still exerting a force.
Production of Force
The actions of muscles are what produce body force. The stronger the muscles the more force that body is capable of producing. All the muscles in a muscle group or groups must be applied in the same direction and in proper sequence to produce the greatest force. The principles of stability and laws of motion must be observed in the performance to get the greatest force.
Force also must be produced to propel an object. The same principles apply in this as the last one. For maximum force the body should be rotated at the hips, shoulders, arms, and hands in sequential order. The summation of these forces will produce max force and a follow-through is necessary to avoid jerky movements and reduce possible injury.
Application of Force
The force of an object is most effective when it is applied in the direction that the object is to travel. To project an object or the body forward most efficiently, the force should be applied through the center of the object in a forward motion. To move body upward, the body must be straight and the force must be applied upward through the center of the body.
In throwing an object three main factors of concern are:
1) Speed of throw- the speed depends on the speed of the hand at the moment of release of the object. The speed can be increased by lengthening it to it s fullest, rotating the body, shifting the weight properly, and taking a step in the direction of the throw. Movements must be done in a continuous motion to maintain momentum.
2) Distance of the throw- Distance of a throw will be affected by the pull of gravity and air resistance. The distance an object will travel will depend on angle of release and the force impaired in the throw. Gravity and air resistance will affect objects less if they are thrown at an angle approximately 45 degrees.
3) Direction that the object will travel-depends on the point of release of the object. The release must be in a point in the arc of the arm that is tangent to the target. The throwing arm should be moved at a flatter arc at the time of release to better achieve the desired angle of release.
In addition to gravity, and air resistance, the flight of thrown and batted object is also affected but the spin of the object.
Absorption of Force
The impact of the force should be gradually reduced, and it should be spread over as large of an area as possible.
Concepts
1. The more muscles that are used, the greater the force that is produced (provided of course that they are the same size muscles.)
2. The more elasticity or stretch a muscle is capable of, the more force it can supply. Each working muscle should be stretched fully to produce the greatest force.
3. When objects are moved, the weight of the object should be pushed or pulled through the center and in the direction that they are to be moved.
4. When heavy objects are moved or thrown, the force of the muscle should be used in a sequential manner. For example, the order in throwing should be trunk rotation, shoulder, upper arm lower arm hand and fingers.
5. When body parts (arms and legs) or implements such as bats and paddles are used. They should be extended completely when making contact with an object to be propelled. This creates a long movement arm, thereby creating the greatest force; the implements should be gripped at the end.
6. When receiving or absorbing the force of a thrown object, a fall or kick the largest possible area should be used to absorb the to absorb the force.
7. The absorption of force should be spread out as long as possible by recoiling or giving at the joints involved in the movement.
8. Objects should be thrown at an angle of appox. 45 degrees for the best possible distance. The take off angle of the body for distance jumps should also be 45 degrees.
9. If a ball spins in one direction, it will go in that direction.
10. Objects must be releases at a point where the hand is tangent to the desired flight of the object.
11. The eyes should be focused on the target.
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