Реферат: The Tennis Serve Essay Research Paper The

In the tennis serve as observed in pictures D – F, during the sticking motion both feet are in contact with the ground to provide maximum to the ball, even though the bodies extended and looks like it could go airborne.

Total force is equal to the sum of the forces of each body segment contributing to the act, if the forces are applied in a single direction and in the proper sequence with correct timing. If the variables sequence, timing, and direction are not all applied correctly together the total force will be minimal. During the action phase, pictures D-F, in the tennis serve total force is achieved by the extension of the arms, legs and trunk along with the timing of the movement of the racket arm in striking the ball, and also the leaning forward of the body.

Force applications should be constant and as even as possible. The force applications should be this way so that maximum force can be used to overcome the resistance of gravity and air or water, and minimum force can be used to overcome inertia.

The relationship between constant force over a greater distance and resulting velocity is a positive one. When the distance over which a force is applied increases, so does the velocity. During the prep phase, pictures A-C, the extension of the racket arm is done to create the distance in which greater velocity will occur and this resulting in a greater striking force of the tennis ball.

Resulting movement depends on the direction and magnitude of the acting forces. If two of these forces act in the same general direction, the direction of the resulting force is somewhere between the two, and the magnitude of the resulting force is more than either, but not as much as the total of the two contributing forces. During the action phase, pictures D-F, the force of the arm, body and racket hitting the ball forward along with gravity pulling it downward, the ball’s flight, although going forward is also going down. This path of the ball is the between result of the two forces acting upon it.

The relationship of muscle length and resulting force is that, the longer the muscle is, the greater the increase in force of that muscle. During the prep phase, pictures A-C, the muscles in the body and the racket arm are tensed or put on stretch to increase the length of the muscle to produce greater force.

The relationship of linear speed to lever length is positive. This means that when a lever gets longer the linear speed gets faster, thus increasing the striking force. During the action phase, pictures D-F, the extension of the levers of the body and racket arm increases the linear speed, resulting in greater striking force of the tennis ball.

Emphasis on proper follow through eliminates the tendency to decelerate a throwing or striking action prior to its completion. Some other benefits of a proper follow through would be to maintain balance and to protect the joint by gradually slowing the body parts. In any case, once contact is broken with the object, follow through actions has no influence on the flight of the object.

There are some external forces that can be used to benefit performance, like water resistance, friction, gravity, and air resistance. Having the correct shoe for the correct playing surface can be very helpful because it could help reduce friction resulting in greater speed. Using gravity and air resistance when striking the tennis ball could be used in the placing of the ball to make it harder for the opponent to hit it.

The relationship of air/water resistance and velocity is that if the velocity at which a body travels is increased by two, the air/water resistance against it will increase by four. During the action phase, pictures D-F, when the tennis ball travels at a certain speed the air resistance is squared. This intern can affect the flight of the ball.

Centrifugal force is only experienced during a rotational (angular) or curvilinear motion. It results from the tendency for an object to continue in a straight line instead of a curved path. It is counteracting by forces (usually muscular) which, if effective, equal or exceed the centrifugal force and tend to maintain the object to continue in its curved path. This counteracting force is centripetal force. In the case of a freely moving body, as velocity increases, centrifugal force increases. Additional weight also increases centrifugal force. The smaller the radius of a curved path, the greater the centrifugal force with the same velocity. During the action phase, pictures D-F, the half circle motion of the racket arm, when in the process of hitting the ball, wants to go in a straight line but the muscles keep it from doing that. Instead, it brings the racket around to strike the ball at the peak height of the ball toss.

A force from a blow can be diminished by distributing the force over either a greater time (and distance) or area, or both. During the action phase, pictures D-F, the size of the racket head determines the distributing of the force of the tennis ball. The bigger the racket head the more the force of the ball is diminished.

In catching an object, the object’s momentum is dissipated by eccentric muscular contractions allowing the joints to move through controlled flexion; and while momentum is being reduced, body parts flex to grasp the object securely. This principle is not found in the tennis serve because there is no object being caught.

If the application is directly through the projectile’s center of gravity, only linear motion results from the force. As the projecting force is moved farther from the center of gravity, rotary motion of the object increases at the expense of linear motion. If the force is below the object’s center of gravity, backspin results. If the force is above the object’s center of gravity, topspin results. The striking of the ball above or below it’s center of gravity which can intern result in topspin or backspin which can change the direction of the ball when it hits the court and also in the air.

The force of gravity on a object starts to diminish it’s vertical velocity as soon as contact is broken. The factors that determine how soon gravity will cause the object to descend are weight, amount of force driving it upward, and the effect of air resistance on the object.

The relationship of speed and air resistance is that as speed increases air resistance plays a more significant role. Objects that are less dense and streamlined are influenced less by air resistance, and the less surface area an object presents, the less will be the effect of air resistance on the object. The tennis ball being somewhat small, round, hollow, and fuzzy, makes it less dense, more streamlined, and it presents less surface area. This all intern makes the tennis ball a pretty streamlined.

The optimal angle for maximum distance when the beginning and end points are at the same level is 45 degrees. The effects of a less than optimal angle results in little distance. The effect of a greater then optimal angle can also result in little distance.

When starting points are above or below ending points, reduce angle to get maximum distance. Since the greatest angle for projection is 45 degrees, the tennis serve is struck downward as close to 45 degrees as possible.

The relationship of the angle of incidence to the angle of reflection is equal. This means that the angle at which the object approaches a surface is equal to the angle at which it leaves that surface. The factors that could change this would be irregular shapes of the two colliding surfaces, the force resulting from elasticity of the object, and the spin of the object both during and after contact. If all else is constant , the angle the tennis ball hits the ground is the angle it will project of the ground. Also in tennis spin will effect the angle.

A highly elastic object will quickly spring back to its original shape after being compressed. The compression of the tennis ball is somewhat moderate but there is also what is called a high compression ball on the market. The elasticity is really high because the ball is made out of rubber, which has a good restitution. The greatest rebound results from a moderately compressed ball with high elasticity. For tennis, a stiff racket and loose strings will produce the greatest elasticity of the ball because the racket if loose does not have great restitution as well as the strings do. Also the ball is highly compressed and has a lot of elasticity to it, to help propel it fast.

An object propelled without spin tends to waver because of air resistance against the object’s irregular surface. A small amount of spin on an object produces a stabilizing effect which tends to hold it on its line of flight. Increased spin will tend to cause the object to curve in the same direction as the spin because of unequal air pressure cause by the spinning. During the serve or contact with the ball spin is added to the ball to throw the opponent off guard. The effect of the spin is to make the opponent change direction very quickly.

To cause an object to spin in the desired direction, the striking implement should be drawn across the object in the direction of the desired spin. Topspin is caused by an implement striking forward-upward. Backspin is produced when the strike is made forward-downward. In the serve topspin is added to draw the ball out or make it jump up. Backspin is added to make the ball fall short, so to make the opponent run to the net.

Topspin causes a lower angle of rebound, a longer bounce, and more roll. Backspin causes a higher angle of rebound, a shorter bounce, and less roll. In the serve these spins are used to throw the opponent off guard and to make them make a quick decision and mess up.

The effects on a vertical surface are different than on a horizontal surface. Topspin causes a higher rebound , backspin causes a lower rebound, right spin causes a rebound to the left, and left spin causes a rebound to the right. Tennis serve does not happen on a vertical surface at all.

The serve is the most important part of tennis, it starts the game and sets the tone for the match. Many of the professionals today have mastered most of theses principles, and these principles can be seen by just watching a match by a valid tennis player.

Biomechanics

The Tennis Serve

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