Javelin
Javelin
The javelin is a sport that is a descendant of the many forms of competitions contested in various parts of the ancient world that involved the throwing of a projectile. The javelin was one of the events that formed a part of the ancient Olympics, and it was included in the inaugural modern Olympic Games in 1896. The javelin is ultimately governed by the umbrella track and field body, the International Amateur Athletics Federation (IAAF). Javelin competitions are best known through the exposure given the sport at the Summer Olympics, where the javelin is an event separately contested by men and women. Javelin also is a part of the biennial World Track and Field championships and various regional athletics meets. Javelin competitions are a part of the National Collegiate Athletic Association (NCAA) annual track and field championships. It is also one of the events that comprise both the decathlon and heptathlon.
The javelin bears a number of technical similarities to the other traditional field sports that require the athlete to throw a projectile as far as possible. The shot put, the hammer throw, and the discus all require the athlete to consider a variety of physical factors, including the effect of wind, the angle at which the object is released, the height at which the object is released, and the speed of the object upon release. It is the specific aerodynamic considerations of the javelin itself that separate this sport from the other throwing events.
The projectile used in javelin consists of three distinct parts—the head, constructed from a light weight metal; the shaft, made from carbon fiber or other composite synthetic materials; and the grip, the portion of the javelin where the object is held by the thrower prior to delivery. Unlike the footwork and resultant body position that is sought by an athlete to produce a successful shot put throw or discus release, the rules of javelin prohibit a spin or twisting of the thrower's body prior to the release of the javelin (the back of the competitor may not face the throwing line at any time prior to the release of the javelin). The projectile is thrown in an overhand fashion after a high speed run to the throwing line by the athlete. The speed of the athlete at the precise moment of delivery, coupled with the arm strength and the technique of the thrower, combine to create the forces that propel the javelin as it leaves the hand of the competitor.
The standard weight of a javelin as prescribed by the rules of the International Amateur Athletics Federation is 1.76 lb (800 g) for men's competition and 1.32 lb (600 g) for women. The javelin shaft is of hollow construction to increase the available surface area exposed to the air in flight. As a general physical proposition, the greater the available surface area of the shaft in relationship to the weight of the projectile, the further the javelin will fly as it benefits from a greater degree of lift.
As the javelin moves through the air, the distance it travels will be significantly affected by the air flow created above and below the projectile. Unlike a discus, which is subject to the lift created by the force of air pressure applied to the underside of the disc (an application of the Bernoulli principle), the flight of the javelin creates a separation of the air flow above and below the shaft. In this air flow separation, the air flowing beneath the shaft is the source of the force providing lift and it helps sustain the flight of the javelin.
The javelin design ensures that the head of the javelin travels lower than the shaft through the air during flight, to ensure a greater likelihood of the head being the first part of the projectile to strike the ground. The javelin should stick into the surface on landing rather than skip horizontally on contact. The rules of javelin prohibit the javelin tail from striking the ground before the head. The desired flight characteristic is achieved by constructing the javelin with the center of gravity (the average location of the javelin's weight) being positioned ahead of the center of pressure of the javelin (the average location of the pressures received by the javelin in flight).
Oscillation is a specific type of vibration that may occur in any object, including those in flight. Oscillation is defined as a periodic motion that occurs between two limits; when a javelin shaft oscillates in flight, it appears to quiver.
Because an oscillating motion occurs perpendicular to the forward path of the javelin, oscillation represents energy delivered by the athlete at the beginning of the throw that is wasted. As a general proposition, the greater the oscillation in the javelin shaft in flight, the less efficient the throw and the shorter the distance the javelin will fly.
To counter the oscillation of the shaft in flight, the thrower imparts spin to the shaft by rotating the shaft on release. The rotation of the shaft counters any perpendicular vibration and it makes the javelin more stable in the air. An elite level javelin thrower will cause the javelin to spin at a rate approaching 25 rotations per second.
Oscillation in the javelin shaft is also minimized by delivering the javelin into the air on the identical vertical plane as the intended flight path of the javelin.
The most prominent physical characteristic of an elite javelin thrower is a strong upper body and shoulder structure, coupled with legs sufficiently powerful to deliver a fast run up at delivery. Coordinated footwork by the athlete as the end of the run up is approached is essential to both preserving the speed developed during the run, as well as delivering the javelin from a stable body position. The athlete will seek to incorporate the maximum allowable twist of the body at release to generate angular momentum that will be directed into the shaft.
see also Archery; Discus; Hammer throw; Shotput.
javelin
jave·lin / ˈjav(ə)lən/ • n. a light spear thrown in a competitive sport or as a weapon. ∎ (the javelin) the athletic event or sport of throwing the javelin: his nearest rival in the javelin.