Tuesday, December 2, 2008
Tuesday, August 12, 2008
well speaking about frenship chec k out this 
picture all about love n frenship
u cant find the any better from a mother than this
when there r lots of obstacles there r no altewrnative
cutest of all 
Monday, August 4, 2008
equipment and systems
metal wire, terrestrial and satellite radio, and optical fibre—employed in the transmission of electromagnetic signals.
Every telecommunications system involves the transmission of an information-bearing electromagnetic signal through a physical medium that separates the transmitter from the receiver. All transmitted signals are to some extent degraded by the environment through which they propagate. Signal degradation can take many forms, but generally it falls into three types: noise, distortion, and attenuation. Noise is the presence of random, unpredictable, and undesirable electromagnetic emissions that can mask the intended information signal. Distortion is any undesired change in the amplitude or phase of any component of an information signal that causes a change in the overall waveform of the signal. Both noise and distortion are commonly introduced by all transmission media, and they both result in errors in reception. The relative impact of these factors on reliable communication depends on the rate of information transmission, on the desired fidelity upon reception, and on whether communication must occur in “real time”—i.e., as in two-way voice telephony and video teleconferencing.
Various modulating and encoding schemes have been devised to provide protection against the errors caused by channel distortion and channel noise. These techniques are described in telecommunication: Analog-to-digital conversion, Channel encoding, and Modulation. In addition to these signal-processing techniques, protection against reception errors can be provided by boosting the power of the transmitter, thus increasing the signal-to-noise ratio (the ratio of signal power to noise power). However, even powerful signals suffer some degree of attenuation, or reduction in power, as they pass through the transmission medium. The principal cause of power loss is dissipation, the conversion of part of the electromagnetic energy to another form of energy such as heat. In communications media, channel attenuation is typically expressed in decibels (dB) per unit distance. Attenuation of zero decibels means that the signal is passed without loss; three decibels means that the power of the signal decreases by one-half. The plot of channel attenuation as the signal frequency is varied is known as the attenuation spectrum, while the average attenuation over the entire frequency range of a transmitted signal is defined as the attenuation coefficient. Channel attenuation is an important factor in the use of each transmission medium.
Wire transmission
In wire transmission an information-bearing electromagnetic wave is guided along a wire conductor to a receiver. Propagation of the wave is always accompanied by a flow of electric current through the conductor. Since all practical conductor materials are characterized by some electrical resistance, part of the electric current is always lost by conversion to heat, which is radiated from the wire. This dissipative loss leads to attenuation of the electromagnetic signal, and the amount of attenuation increases linearly with increasing distance between the transmitter and the receiver.
Wire media
Most modern wire transmission is conducted through the metallic-pair circuit, in which a bundled pair of conductors is used to provide a forward current path and a return current path. The most common conductor is hard-drawn copper wire, which has the benefits of low electrical resistance, high tensile strength, and high resistance to corrosion. The basic types of wire media found in telecommunications are single-wire lines, open-wire pairs, multipair cables, and coaxial cables. They are described below.
Single-wire line
In the early days of telegraphy, a single uninsulated iron wire, strung above ground, was used as a transmission line. Return conduction was provided through an earth ground. This arrangement, known as the single-wire line, was quite satisfactory for the low-frequency transmission requirements of manual telegraph signaling (only about 400 hertz). However, for transmission of higher-frequency signals, such as speech (approximately 3,000 hertz), single-wire lines suffer from high attenuation, radiation losses, and a sensitivity to stray currents induced by random fluctuations in earth ground potentials or by external interference. One common cause of external interference is natural electrical disturbances, such as lightning or auroral activity; another is cross talk, an unwanted transferral of signals from one circuit to another owing to inductive coupling between two or more closely spaced wire lines.
Open-wire pair
In order to overcome the insufficiencies of single-wire transmission, the early telephone industry shifted to a two-wire system called the open-wire pair. In an open-wire pair the forward and return conductors are copper wires that run in parallel and in a common plane. The parallel arrangement produces a balanced transmission circuit that has low sensitivity to faraway interference sources such as lightning. Immunity to such interference is possible because both of the conductors in the open-wire pair, by running in parallel and in the same plane, are at essentially equal distances from the interference source. The source therefore induces equal currents in the forward and return paths, and these currents are effectively canceled out at the receiving end of the line.
It is much more difficult to eliminate cross talk between adjacent open-wire pairs than it is to eliminate interference from a faraway source. In order to ensure equal forward and return currents, all adjacent pairs have to be balanced with respect to one another. In early low-density telephone lines, cross talk was reduced through an ingenious and complicated method of periodically transposing the relative positions of the forward and return conductors in each pair. Transposing the wires equalized the relative positions of adjacent circuits as well as the currents that they induced in one another.
Multipair cable
• Wire transmission media
In multipair cable anywhere from a half-dozen to several thousand twisted-pair circuits are bundled into a common sheath (see Figure 1). The twisted pair was developed in the late 19th century in order to reduce cross talk in multipair cables. In a process similar to that employed with open-wire pairs (described above), the forward and return conductors of each circuit in a multipair cable are braided together, equalizing the relative positions of all the circuits in the cable and thus equalizing currents induced by cross talk.
For many high-speed and high-density applications, such as computer networking, each wire pair is sheathed in metallic foil. Sheathing produces a balanced circuit, called a shielded pair, that benefits from greatly reduced radiation losses and immunity to cross talk interference.
Coaxial cable
• Wire transmission media
By enclosing a single conducting wire in a dielectric insulator and an outer conducting shell, an electrically shielded transmission circuit called coaxial cable is obtained. In a coaxial cable the electromagnetic field propagates within the dielectric insulator, while the associated current flow is restricted to adjacent surfaces of the inner and outer conductors. As a result, coaxial cable has very low radiation losses and low susceptibility to external interference.
In order to reduce weight and make the cable flexible, tinned copper or aluminum foil is commonly used for the conducting shell. Most coaxial cables employ a lightweight polyethylene or wood pulp insulator; although air would be a more effective dielectric, the solid material serves as a mechanical support for the inner conductor.
Applications of wire
Because of the high signal attenuation inherent in wire, transmission over distances greater than a few kilometres requires the use of regularly spaced repeaters to amplify, restore, and retransmit the signal. Transmission lines also require impedance matching at the transmitter or receiver in order to reduce echo-creating reflections. Impedance matching is accomplished in long-distance telephone cables by attaching a wire coil to each end of the line whose electrical impedance, measured in ohms, is equal to the characteristic impedance of the transmission line. A familiar example of impedance matching is the transformer used on older television sets to match a 75-ohm coaxial cable to antenna terminals made for a 300-ohm twin-lead connection.
Coaxial cable is classified as either flexible or rigid. Standard flexible coaxial cable is manufactured with characteristic impedance ranging from 50 to 92 ohms. The high attenuation of flexible cable restricts its utility to short distances—e.g., spans of less than one kilometre, or approximately a half-mile—unless signal repeaters are used. For high-capacity long-distance transmission, a more efficient wire medium is rigid coaxial cable, which was favoured for telephone transmission until it was supplanted by optical fibres in the 1980s. A state-of-the-art rigid coaxial telephone cable is the transatlantic SG series cable; the third cable in the series, called TAT-6, was laid in 1976 by the American Telephone & Telegraph Company (AT&T) between the east coast of the United States and the west coast of France. Capable of carrying 4,200 two-way voice circuits, the SG system has solid-state repeaters embedded in the cable housing at intervals of 9.5 kilometres (5.75 miles) and has equalizers that can be remotely adjusted to compensate for time-varying transmission characteristics.
Long-distance telephone cable is being phased out in favour of higher-performance optical fibre cable. Nevertheless, the last generation of long-distance telephone cable is still used to carry voice communication as well as broadband audio and video signals for cable television providers. For short-distance applications, where medium bandwidth and low-cost point-to-point communication is required, twisted pair and coaxial cable remain the standard. Voice-grade twisted pair is used for local subscriber loops in the public switched telephone network, and flexible coaxial cable is commonly used for cable television connections from curbside to home. Flexible coaxial cable also has been used for local area network interconnections, but it has largely been replaced with lighter and lower-cost data-grade twisted pair and optical fibre.
equipment and systems
metal wire, terrestrial and satellite radio, and optical fibre—employed in the transmission of electromagnetic signals.
Every telecommunications system involves the transmission of an information-bearing electromagnetic signal through a physical medium that separates the transmitter from the receiver. All transmitted signals are to some extent degraded by the environment through which they propagate. Signal degradation can take many forms, but generally it falls into three types: noise, distortion, and attenuation. Noise is the presence of random, unpredictable, and undesirable electromagnetic emissions that can mask the intended information signal. Distortion is any undesired change in the amplitude or phase of any component of an information signal that causes a change in the overall waveform of the signal. Both noise and distortion are commonly introduced by all transmission media, and they both result in errors in reception. The relative impact of these factors on reliable communication depends on the rate of information transmission, on the desired fidelity upon reception, and on whether communication must occur in “real time”—i.e., as in two-way voice telephony and video teleconferencing.
Various modulating and encoding schemes have been devised to provide protection against the errors caused by channel distortion and channel noise. These techniques are described in telecommunication: Analog-to-digital conversion, Channel encoding, and Modulation. In addition to these signal-processing techniques, protection against reception errors can be provided by boosting the power of the transmitter, thus increasing the signal-to-noise ratio (the ratio of signal power to noise power). However, even powerful signals suffer some degree of attenuation, or reduction in power, as they pass through the transmission medium. The principal cause of power loss is dissipation, the conversion of part of the electromagnetic energy to another form of energy such as heat. In communications media, channel attenuation is typically expressed in decibels (dB) per unit distance. Attenuation of zero decibels means that the signal is passed without loss; three decibels means that the power of the signal decreases by one-half. The plot of channel attenuation as the signal frequency is varied is known as the attenuation spectrum, while the average attenuation over the entire frequency range of a transmitted signal is defined as the attenuation coefficient. Channel attenuation is an important factor in the use of each transmission medium.
Wire transmission
In wire transmission an information-bearing electromagnetic wave is guided along a wire conductor to a receiver. Propagation of the wave is always accompanied by a flow of electric current through the conductor. Since all practical conductor materials are characterized by some electrical resistance, part of the electric current is always lost by conversion to heat, which is radiated from the wire. This dissipative loss leads to attenuation of the electromagnetic signal, and the amount of attenuation increases linearly with increasing distance between the transmitter and the receiver.
Wire media
Most modern wire transmission is conducted through the metallic-pair circuit, in which a bundled pair of conductors is used to provide a forward current path and a return current path. The most common conductor is hard-drawn copper wire, which has the benefits of low electrical resistance, high tensile strength, and high resistance to corrosion. The basic types of wire media found in telecommunications are single-wire lines, open-wire pairs, multipair cables, and coaxial cables. They are described below.
Single-wire line
In the early days of telegraphy, a single uninsulated iron wire, strung above ground, was used as a transmission line. Return conduction was provided through an earth ground. This arrangement, known as the single-wire line, was quite satisfactory for the low-frequency transmission requirements of manual telegraph signaling (only about 400 hertz). However, for transmission of higher-frequency signals, such as speech (approximately 3,000 hertz), single-wire lines suffer from high attenuation, radiation losses, and a sensitivity to stray currents induced by random fluctuations in earth ground potentials or by external interference. One common cause of external interference is natural electrical disturbances, such as lightning or auroral activity; another is cross talk, an unwanted transferral of signals from one circuit to another owing to inductive coupling between two or more closely spaced wire lines.
Open-wire pair
In order to overcome the insufficiencies of single-wire transmission, the early telephone industry shifted to a two-wire system called the open-wire pair. In an open-wire pair the forward and return conductors are copper wires that run in parallel and in a common plane. The parallel arrangement produces a balanced transmission circuit that has low sensitivity to faraway interference sources such as lightning. Immunity to such interference is possible because both of the conductors in the open-wire pair, by running in parallel and in the same plane, are at essentially equal distances from the interference source. The source therefore induces equal currents in the forward and return paths, and these currents are effectively canceled out at the receiving end of the line.
It is much more difficult to eliminate cross talk between adjacent open-wire pairs than it is to eliminate interference from a faraway source. In order to ensure equal forward and return currents, all adjacent pairs have to be balanced with respect to one another. In early low-density telephone lines, cross talk was reduced through an ingenious and complicated method of periodically transposing the relative positions of the forward and return conductors in each pair. Transposing the wires equalized the relative positions of adjacent circuits as well as the currents that they induced in one another.
Multipair cable
• Wire transmission media
In multipair cable anywhere from a half-dozen to several thousand twisted-pair circuits are bundled into a common sheath (see Figure 1). The twisted pair was developed in the late 19th century in order to reduce cross talk in multipair cables. In a process similar to that employed with open-wire pairs (described above), the forward and return conductors of each circuit in a multipair cable are braided together, equalizing the relative positions of all the circuits in the cable and thus equalizing currents induced by cross talk.
For many high-speed and high-density applications, such as computer networking, each wire pair is sheathed in metallic foil. Sheathing produces a balanced circuit, called a shielded pair, that benefits from greatly reduced radiation losses and immunity to cross talk interference.
Coaxial cable
• Wire transmission media
By enclosing a single conducting wire in a dielectric insulator and an outer conducting shell, an electrically shielded transmission circuit called coaxial cable is obtained. In a coaxial cable the electromagnetic field propagates within the dielectric insulator, while the associated current flow is restricted to adjacent surfaces of the inner and outer conductors. As a result, coaxial cable has very low radiation losses and low susceptibility to external interference.
In order to reduce weight and make the cable flexible, tinned copper or aluminum foil is commonly used for the conducting shell. Most coaxial cables employ a lightweight polyethylene or wood pulp insulator; although air would be a more effective dielectric, the solid material serves as a mechanical support for the inner conductor.
Applications of wire
Because of the high signal attenuation inherent in wire, transmission over distances greater than a few kilometres requires the use of regularly spaced repeaters to amplify, restore, and retransmit the signal. Transmission lines also require impedance matching at the transmitter or receiver in order to reduce echo-creating reflections. Impedance matching is accomplished in long-distance telephone cables by attaching a wire coil to each end of the line whose electrical impedance, measured in ohms, is equal to the characteristic impedance of the transmission line. A familiar example of impedance matching is the transformer used on older television sets to match a 75-ohm coaxial cable to antenna terminals made for a 300-ohm twin-lead connection.
Coaxial cable is classified as either flexible or rigid. Standard flexible coaxial cable is manufactured with characteristic impedance ranging from 50 to 92 ohms. The high attenuation of flexible cable restricts its utility to short distances—e.g., spans of less than one kilometre, or approximately a half-mile—unless signal repeaters are used. For high-capacity long-distance transmission, a more efficient wire medium is rigid coaxial cable, which was favoured for telephone transmission until it was supplanted by optical fibres in the 1980s. A state-of-the-art rigid coaxial telephone cable is the transatlantic SG series cable; the third cable in the series, called TAT-6, was laid in 1976 by the American Telephone & Telegraph Company (AT&T) between the east coast of the United States and the west coast of France. Capable of carrying 4,200 two-way voice circuits, the SG system has solid-state repeaters embedded in the cable housing at intervals of 9.5 kilometres (5.75 miles) and has equalizers that can be remotely adjusted to compensate for time-varying transmission characteristics.
Long-distance telephone cable is being phased out in favour of higher-performance optical fibre cable. Nevertheless, the last generation of long-distance telephone cable is still used to carry voice communication as well as broadband audio and video signals for cable television providers. For short-distance applications, where medium bandwidth and low-cost point-to-point communication is required, twisted pair and coaxial cable remain the standard. Voice-grade twisted pair is used for local subscriber loops in the public switched telephone network, and flexible coaxial cable is commonly used for cable television connections from curbside to home. Flexible coaxial cable also has been used for local area network interconnections, but it has largely been replaced with lighter and lower-cost data-grade twisted pair and optical fibre.
Automotive Insurance, a contract by which the insurer assumes the risk of any loss the owner or operator of a motor vehicle may incur through damage to property or persons as the result of an accident. There are many specific forms of motor-vehicle insurance, varying not only in the kinds of risk that they cover but also in the legal principles underlying them.
Liability insurance pays for damage to someone else's property or for injury to other persons resulting from an accident for which the insured is judged legally liable; collision insurance pays for damage to the insured car if it collides with another vehicle or object; comprehensive insurance pays for damage to the insured car resulting from fire or theft and also from many other causes; medical-payment insurance covers medical treatment for the policyholder and his passengers.
In many countries, other approaches to automobile accident insurance have been tried. These include compulsory liability insurance on a no-fault basis and loss insurance (accident and property insurance) carried by the driver or owner on behalf of any potential victim, who would recover without regard to fault.
Most existing no-fault plans are limited in the sense that they usually permit the insured party to sue the party at fault for damages in excess of those covered by the plan and permit insuring companies to recover costs from each other according to decisions on liability. Total no-fault insurance, on the other hand, would not permit the insured to enter tort liability actions or the insurer to recover costs from another insurer.
Thursday, July 31, 2008
Jordanka Donkova (centre) of Bulgaria leading Cornelia Oschkenat (left) of East Germany to win the …
also called track-and-field sports or track and field a variety of competitions in running, walking, jumping, and throwing events. Although these contests are called track and field (or simply track) in the United States, they are generally designated as athletics elsewhere. This article covers the history, the organization, and the administration of the sports, the conduct of competitions, the rules and techniques of the individual events, and some of the sports' most prominent athletes.
Track-and-field athletics are the oldest forms of organized sport, having developed out of the most basic human activities—running, walking, jumping, and throwing. Athletics have become the most truly international of sports, with nearly every country in the world engaging in some form of competition. Most nations send teams of men and women to the quadrennial Olympic Games and to the official World Championships of track and field. There also are several continental and intercontinental championship meets held, including the European, Commonwealth, African, Pan-American, and Asian.
Within the broad title of athletics come as many as two dozen distinct events. These events, generally held outdoors, make up a meet. The outdoor running events are held on a 400-metre or 440-yard oval track, and field events (jumping and throwing) are held either inside the track's perimeter or in adjacent areas.
In many parts of the world, notably the United States, Canada, and Europe, the sport moves indoors during the winter; because of limited space, some events are modified and several are eliminated altogether.
Also within the general scope of track-and-field athletics come separate but related competitions that are not contested on the track. Cross-country running competition is carried out on various types of countryside and parkland. Marathons and races of other long distances are run on roads, and the long-distance race walks are contested on measured road courses. The rules followed by all organized competitions are established and enforced by the International Association of Athletics Federations (IAAF) and its member body from each nation. The IAAF also ratifies all world records.
History
Origin and early development
There is little in the way of definitive records of athletics' early days as organized sport. Egyptian and Asian civilizations are known to have encouraged athletics many centuries before the Christian era. Perhaps as early as 1829 BC, Ireland was the scene of the Lugnasad festival's Tailteann Games, involving various forms of track-and-field activity. The Olympic Games of Greece, traditionally dated from 776 BC, continued through 11 centuries before ending about AD 393. These ancient Olympics were strictly male affairs, as to both participants and spectators. Greek women were reputed to have formed their own Heraea Games, which, like the Olympics, were held every four years.
Athletics as practiced today was born and grew to maturity in England. The first mention of the sport in England was recorded in 1154, when practice fields were first established in London. The sport was banned by King Edward III in the 1300s but revived a century later by Henry VIII, reputed to be an accomplished hammer thrower.
Modern development
The development of the modern sport, however, has come only since the early 19th century. Organized amateur footraces were held in England as early as 1825, but it was from 1860 that athletics enjoyed its biggest surge to that date. In 1861 the West London Rowing Club organized the first meet open to all amateurs, and in 1866 the Amateur Athletic Club (AAC) was founded and conducted the first English championships. The emphasis in all these meets was on competition for “gentlemen amateurs” who received no financial compensation. In 1880 the AAC yielded governing power to the Amateur Athletic Association (AAA).
The first meet in North America was held near Toronto in 1839, but it was the New York Athletic Club, formed in the 1860s, that placed the sport on a solid footing in the United States. The club held the world's first indoor meet and helped promote the formation in 1879 of the National Association of Amateur Athletes of America (NAAAA) to conduct national championships. Nine years later the Amateur Athletic Union (AAU) took over as national governing body, amid reports that the NAAAA was lax in enforcing amateurism.
Athletics was well established in many countries by the late 1800s, but not until the revival of the Olympic Games in 1896 did the sport become truly international. Although begun modestly, the Olympics provided the inspiration and standardizing influence that was to spread interest in athletics worldwide. In 1912 the International Amateur Athletic Federation (IAAF) was founded, and by the time that organization celebrated its 75th anniversary in 1987 it had more than 170 national members. Its rules applied only to men's competition until 1936, when the IAAF also became the governing body of women's athletics.
Major international competitions before World War II included the Olympics, the British Empire Games, and the European Championships, but after the war athletics experienced its greatest period of growth, taking root especially in the developing countries. By the 1950s world-class athletes from African, Asian, and Latin American nations were enjoying great success at international meets.
Organization and tournaments
Top-level competition in athletics is still restricted to the amateur athlete, although the definition of “amateur” continues to evolve. The IAAF over time has reduced its definition of an amateur athlete to the simplest possible terms: “An amateur is one who abides by the eligibility rules of the IAAF” is the complete rule, allowing for change whenever the federation alters any of its other rules.
Until the 1980s the IAAF attempted to keep its athletes from benefiting financially from the sport. This was always a struggle, however, as star athletes and eager meet promoters managed to circumvent the rules. So did entire nations: eastern European countries provided government aid to athletes, other countries encouraged military personnel to concentrate on track-and-field training, and U.S. athletes received college scholarships in return for their skills.
Financial aid was made acceptable in the 1980s through the use of trust funds. Athletes were permitted to accept payment for appearing in competition, for performing well, for appearing in television commercials, or for other sport-related activities. The money was placed in trust; training expenses could be charged to the fund, with the remaining funds, if any, going to the athlete on retirement from competition. Some athletes were reported to have made several hundred thousand dollars a year under the new system.
The primary functions of the IAAF are to maintain a set of rules that are uniform throughout the world, to approve world records for outdoor and indoor competition, and to promote international athletics. While continuing to administer athletics competition in the Olympic Games, the IAAF began its own quadrennial World Championships in 1983, established World Cup competitions, and established walking, cross-country, marathon and other road races, indoor track and field, and junior competitions.
Each IAAF member nation has its own set of rules and maintains its own set of records in line with international guidelines. The amateur athletic federations of individual countries conduct their own national championships.
In the United States, for example, The Athletic Congress (TAC) alone has the power to select international teams (except for the Olympic team, which is under the jurisdiction of the United States Olympic Committee), to establish rules, and to accept or reject records. It also conducts the national championships and other competitions. Meets in which participation is restricted to college or university athletes usually are governed by the rules of the National Collegiate Athletic Association (NCAA), National Association of Intercollegiate Athletics (NAIA), or one of two junior (two-year) college groups. Most secondary schools in the United States come under the aegis of the National Federation of State High School Athletic Associations.
The details of the conduct of athletics competitions vary with the location and the level and type of meet. To a great degree the basic sport has been standardized by the rules of the IAAF. Outdoor track events take place on the 400-metre (about 440-yard) oval running track. Track compositions differ greatly. Once almost all tracks were of natural materials (dirt, clay, cinders, and crushed brick being the most common), but all major competition tracks now are made of synthetic materials. The synthetic track provides more consistent and faster footing in all weather conditions. Field event performers also benefit from improved footing; jumpers and javelin throwers perform on the same materials used for synthetic tracks, while the throwers of the shot, discus, and hammer work in circles made of concrete.
Indoor track meets adapt themselves to widely varying and often limiting conditions. Tracks range in size generally from 150 to 200 metres or 160 to 220 yards and have synthetic surfaces over wood. Some tracks have banked curves, others are unbanked. Cross-country running utilizes any terrain that is available—parks, golf courses, farmland. The prescribed IAAF distance in international races for men is approximately 12,000 metres (7.5 miles) and for women 4,000 metres (2.5 miles). Road events include walking, marathon, and other road runs of widely varying distances.
Meets
Equipment
Every event has items of equipment that are essential to the conduct of the event. All athletes, for example, require shoes that give traction and protection with minimum weight. Other items of equipment include the starting blocks used by sprinters and hurdlers, hurdles, vaulting poles, and the implements employed in the various throwing events.
Timing and measurements
Exacting timing and measurement of performances are a vital part of athletics, not only to determine winners at the meet in question but also to provide marks that can be compared for record purposes. Fully automatic timing, using photography, is required for world records and all major competitions. Timing, once done in fifths of a second and then in tenths, now is done in hundredths of a second. By rule, an aiding wind of more than 2 metres per second (4.473 miles per hour) nullifies a record time in distances up to 200 metres. Metric measurements are required for both track and field events, even in the United States. The only English-measure distance that remains popular is the one-mile run. With the 1987 inauguration of the World Indoor Championships, the IAAF began accepting indoor records.
Presentation
Athletics meets differ greatly in presentation. The typical school, university, or club meet is of one-day duration. Conference meets generally last two days, while national championships require three to four days to accommodate large numbers of athletes. The Olympic Games and World Championships are scheduled for eight days of athletics competition.
All track events begin with the firing of a gun. In races of one lap or less the runners remain in their marked lanes for the entire distance. In longer events the runners may ignore the lane markers and run as close to the inside edge of the track as is prudent. The runner whose torso reaches the winning line first is the winner.
Field events have two types of qualifying competitions. In the smaller meets all participants are allowed three attempts, with the top six to nine athletes getting three more. In the larger meets there is a qualifying round from which about 12 athletes advance to the finals, at which stage the remaining competition proceeds in the same manner as in the smaller meets. The exceptions in field event competition are the vertical jumps—the high jump and pole vault. Jumpers are given three tries at each height; three consecutive misses cause elimination.
Although athletics is basically an individual sport, team scoring is sometimes important. Dual meets are always scored, but there are no official scores for multi-team international meets, such as the Olympic Games. Conference and national meets among universities also are scored officially. The points allotted to individual events and places vary from meet to meet. A national competition may award 10 points for first place, 8 for second, and so on. Similarly, an international dual meet awards 5 points for first place, 3 for second, 2 for third, and 1 for fourth. The team with the highest point total wins the meet. Cross-country meets always are scored, with the winner getting 1 point, second place 2 points, etc., the low score winning.
Runners have a chance to compete year-round. The indoor season lasts from January through March; the outdoor competition lasts until June for schools and colleges, with the higher-level individual competitors participating in track through September. In the United States autumn is given over to cross-country running. International cross-country is held in winter.
Conflicts and controversies
Athletics, occupying centre stage at all international games, generates its share of conflicts. Until the IAAF's trust-fund system there was continual concern about athletes earning money by violating rules. From about 1970 the question of drug usage has been a major issue. Athletes are forbidden to use a number of drugs that are said to improve performance. Testing for such use is required at the major meets, and, while the great majority of athletes tested are found to be free of banned drugs, each year a small number of athletes are found guilty of violating the drug rule and are suspended from competition, usually for 18 months. Most frequently the violators have used anabolic steroids in an attempt to increase muscle size and strength.
Events
As many as 25 events may make up a men's meet; women compete in a few less. The men's track events at championship meets generally include the 100-, 200-, 400-, 800-, 1,500-, 5,000-, and 10,000-metre runs; the 3,000-metre steeplechase; the 110- and 400-metre hurdles; and the 400- and 1,500-metre relays. The field events usually include the high jump, pole vault, long jump, triple jump, shot put, discus throw, hammer throw, and javelin throw. The decathlon, combining 10 track-and-field events, is also featured. Women run much the same schedule, with 100-metre instead of 110-metre hurdles, but do not compete in the steeplechase, pole vault, or hammer throw. They compete in the heptathlon (seven events) rather than the decathlon, and both men and women run the marathon. Women walk up to 10,000 metres and men up to 50,000 metres.
Running
The sprints
The relatively short sprint distances, ranging up to 400 metres, require a sustained top speed. Originally all sprinters started from a standing position, but in the 1880s the crouch start was invented, and it became a rule that sprinters must start with both feet and both hands on the track. The introduction of the adjustable starting block aided the quick start, critical in the sprints.
The current record holder at 100 metres generally is considered to be “the fastest human.” Holding that title have been such champions as Eddie Tolan, Jesse Owens, Bobby Morrow, Bob Hayes, and Carl Lewis (all of the United States), Valeriy Borzov (U.S.S.R.), Linford Christie (U.K.), and Donovan Bailey (Canada). Maurice Greene of the United States set a record time of 9.79 seconds at a 1999 meet in Athens, Greece. Outstanding women sprint champions have included Fanny Blankers-Koen (The Netherlands), who won four gold medals in the 1948 Olympics, Wilma Rudolph (U.S.), who won three in 1960, Marita Koch (East Germany), who was a winner at all three sprint distances, and Florence Griffith Joyner (U.S.), who set world records at 100 and 200 metres in 1988.
The 400 metres is run in lanes all the way; distance is equalized by a staggered start, the sprinters being spaced progressively farther up the track based on the distance their lane is from the inside edge. Outstanding in this event were Lee Evans (U.S.), whose 43.86-second mark remained the world record 20 years after he set it in 1968, Alberto Juantorena (Cuba), whose 44.26-second time in the 1976 Olympics was the fastest without the aid of high altitude, and Michael Johnson (U.S.), whose world record time of 43.18 seconds was set at the 1999 World Championships in Sevilla, Spain. Jarmila Kratochvilova (Czechoslovakia) won a rare double victory in the women's 400- and 800-metre events at the 1983 World Championships.
Middle-distance running
The longer the race, the more endurance is needed. The middle-distance events, in this discussion, range from 800 to 2,000 metres. Some authorities regard the 3,000-metre race as middle-distance.
Middle-distance runners usually are able to perform well at either the shorter or the longer distances. Racing tactics, including pacing, are more important at these than at any other distances. Even though it is no longer a championship event, the mile is still a glamour event. The first athlete to run a mile in less than four minutes—Roger Bannister of England in 1954—captured world attention. A “sub-four” is still a notable time, even though it is now routinely accomplished by the world's top runners. Other great middle-distance runners include Paavo Nurmi (Finland), who won both the 1,500 (the metric “mile”) and 5,000 metres on the same day in the 1924 Olympics, Sebastian Coe (U.K.), who won two Olympic gold medals at 1,500 metres and two silver at 800 metres, Noureddine Morceli (Algeria), who won two world championships and an Olympic gold medal in the 1,500 metres, and Hicham El Guerrouj (Morocco), who set outdoor and indoor world records in the 1,500 metres and the mile. Two Soviet women created memorable middle-distance records. Tatyana Kazankina won five world records, while Lyudmila Bragina established eight. Mary Decker Slaney (U.S.) also won consistently at the middle distances.
Long-distance running
There is some difference of opinion over the dividing line between middle-distance and long-distance runs. The long-distance events considered here are those ranging from 3,000 metres upward; they include the marathon, steeplechase, cross-country, and road runs. The marathon is the longest event for which the IAAF keeps records. Speed becomes an even less important factor in the longer runs, pace and endurance correspondingly more so. The longer the run, the less likely the burst of speed known as the “finishing kick” at the end of the race.
Runners may also overlap the long- and middle-distance events. Nurmi, Gunder Hägg (Sweden), and Said Aouita (Morocco) all set world records at both 1,500 and 5,000 metres. Nurmi won at all distances longer than 1,000 metres except the marathon. Distance runners provide the most prolific record setters, including Nurmi, Ron Clarke (Australia), Kip Keino (Kenya), Haile Gebrselassie (Ethiopia), and Emil Zátopek (Czechoslovakia), the last of whom performed the remarkable feat of winning the marathon and the 5,000- and 10,000-metre races at the 1952 Olympic Games. The longer races for women have been slow to develop, but a number of runners have been able to compete at various distances, including Ingrid Kristiansen (Norway).
The steeplechase combines long-distance running with hurdling, each runner being required to clear seven water jumps and 28 hurdles in a 3,000-metre course. Although hurdling is an important aspect of the event, by far the greatest need is the ability to run the distance. Steeplechase competitors are often specialists, but there are examples of fine distance runners who have successfully overcome more experienced hurdlers. Henry Rono (Kenya), one of the most successful at the steeplechase, also held world records at 3,000, 5,000, and 10,000 metres.
The marathon was a key event at the first modern Olympic Games in 1896, and it has become a major attraction of the Olympics and other international contests. The race originally commemorated the feat of a Greek soldier who in 490 BC supposedly ran from Marathon to Athens to bring news of the Greek victory over the Persians. At 26.22 miles (42,186 metres) the marathon is the longest race of the track meet. Hannes Kolehmainen (Finland) and Zátopek are two of the more memorable marathoners.
Hurdling
The hurdling events combine sprinting with negotiating a series of obstacles called hurdles. Men run the 110-metre high hurdles over 10 barriers 106.7 cm (42 inches) high and 9.14 metres (10 yards) apart. The 400-metre intermediate hurdles also covers 10 hurdles, but 91.4 cm (36 inches) in height and 35 metres (38.29 yards) apart. Women now run both the 100-metre high and 400-metre hurdles. A hurdler may knock down any number of hurdles but is disqualified if he runs out of his lane or uses his hands to knock over hurdles. The object is to make the hurdling action smooth and rhythmic so as not to disrupt forward progress.
High hurdlers need excellent speed, most champions also being good sprinters. An outstanding example is Harrison Dillard (U.S.), who won the 100-metre flat race in the 1948 Olympics and the high hurdles in the 1952 Games. Intermediate hurdlers also combine speed with hurdling ability. Glenn Davis (U.S.), who won both the 1956 and 1960 Olympics, was a world-record breaker on the flat as well as over the hurdles. Edwin Moses (U.S.) virtually revolutionized the event with his unusual 13-stride (between hurdles) technique. He also won two Olympics and achieved a winning streak lasting nearly 10 years.
Relays
The relays involve four runners per team, each member carrying a baton for 25 percent of the total distance before passing it to the next team runner. Two events, the 4 × 100- and 4 × 400-metre relays, are standard. They are included both in low-level dual meets and in the Olympic Games and the IAAF World Championships. Speed is essential in both events, and the ability to pass the baton well is especially crucial in the shorter event, where each runner covers 100 metres. Exchanging the baton while running about 25 miles per hour brings to the event a quality of suspense. Many races have been won or lost by the quality of baton passing. Other relay events—the 4 × 200-, 4 × 800-, and 4 × 1,500-metres—are run much less frequently.
Walking
This event, also called race walking, is relatively minor. Aside from the Olympic and other multinational competitions, it is seldom a part of track meets. Olympic competition is over 20,000 and 50,000 metres, while other distances are used in individual competitions.
Jumping
Men and women compete in four jumping events: the high jump, long jump, triple jump, and pole vault.
The high jump
There is one basic rule for high jumping: the jumper must leave the ground from one foot, not two. The object is to clear a thin bar perched atop two standards, and the jumper remains in the competition as long as he does not have three consecutive misses. Jumpers may enter the competition at any height above the minimum height and are allowed to pass any height as the bar is raised to new levels. Inflated or foam-rubber landing pits have replaced dirt and sawdust pits. The modern pits are of value because jumpers often land on the back of the shoulders and neck.
Jumping styles evolved in the 20th century with techniques called the scissors, eastern cut-off, western roll, and straddle (or belly roll) preceding the Fosbury flop. Named for its inventor, Dick Fosbury (U.S.), the 1968 Olympic champion, the flop involves an approach from almost straight ahead, then twisting on takeoff and going over headfirst with the back to the bar. Charles Dumas (U.S.), a notable example of the straddle jumpers, in 1956 became the first man to clear 7 feet (2.13 metres). Valeriy Brumel (U.S.S.R.) held the high-jump record for 10 years using the straddle jump. A woman jumper, Iolanda Balas (Romania), achieved remarkable feats in the event, establishing 13 world records and a winning streak of 140 meets.
The pole vault
Pole-vaulting is conducted along the lines of the high jump; i.e., vaulters attempt to vault over a crossbar placed on uprights, they have three tries at each height, and they land in an inflated or composition pit.
The vaulter runs down a runway for about 45 metres (150 feet) carrying a pole. After planting the end of the pole in a box that is sunk below ground level, the vaulter leaves the ground and pulls himself upward until he is almost doing a handstand on the pole. He twists as he nears the crossbar and arches over it feetfirst and facedown.
The first poles, of solid ash, cedar, or hickory, were heavy and cumbersome. Once the bamboo pole was introduced in 1904, it was quickly adopted. Records set with bamboo lasted until 1957, when records were set with an aluminum pole and a steel pole; these were followed by the fibreglass pole in the 1960s.
The dominant vaulter of the bamboo era was Cornelius Warmerdam (U.S.), who scored six world records; he was the first vaulter to go over 15 feet (4.6 metres), and he set a record of 15 feet 7.75 inches that lasted for 15 years. The constant improvement of fibreglass poles helped vaulters such as Sergey Bubka (Ukraine) push the record over 20 feet in the 1990s. In the 1990s the IAAF added women's pole vault to the competition roster, and Stacy Dragila (U.S.) became the event's first women's world and Olympic champion.
The long jump
Long jumping, formerly called broad jumping, is the least complicated of the field events. Speed is the most essential ingredient for a successful jump. Jumpers make their approach down the runway at nearly top speed, plant a foot on the takeoff board, and leap into the air. A legal jump requires that no part of the forward foot extend beyond the board. The most popular long-jumping style is called the “hitch-kick,” in which the runner seemingly walks in air.
Bob Beamon (U.S.) breaking the world record in the long jump at 8.90 metres (29.2 feet) during the …
Three distinct landmarks stand out in the history of long jumping. The first of these was the achievement of Jesse Owens (U.S.), who on May 25, 1935, jumped 8.13 metres (26 feet 8.25 inches), a record that endured for 25 years. The second was Bob Beamon's (U.S.) leap of 8.90 metres (29 feet 2.5 inches), a jump that exceeded the old world record by 55 cm (21.5 inches). The third feat came in 1991, when Mike Powell (U.S.) broke Beamon's 23-year record with a jump of 8.95 metres (29 feet 4.5 inches).
Notable among the women jumpers are Heike Drechsler (Germany) and Jackie Joyner-Kersee (U.S.), both of whom leaped over 7 metres (23 feet).
The triple jump
Once known as the hop, step, and jump, the triple jump includes three distinct segments of action. The jumper comes down the runway and bounds off a takeoff board, similar in style to but a little slower than long jumpers. The first segment involves the jumper executing a hop by landing on the same foot from which he took off. Then he takes a step, landing on the other foot, and concludes with a jump into the sand pit.
Among the outstanding competitors, Adhemar da Silva (Brazil) won two Olympics and set five world records; Jozef Schmidt (Poland), also a two-time Olympic champion, set a record in 1960 of 17.03 metres (55 feet 10.5 inches) and was the first to go over the 17-metre barrier; and Viktor Saneyev (U.S.S.R.) had three world records and three Olympic wins and one second place. Women began competing in the triple jump in the mid-1980s.
Throwing
The four standard throwing events—shot, discus, hammer, and javelin—all involve the use of implements of various weights and shapes that are hurled for distance.
The shot put
The putting action is best described as shoving the shot, because the rules require that the arm may not extend behind the shoulders during the putting action. The spherical shot is made of metal. The men's shot weighs 7.26 kg (16 pounds) and is 110–130 mm (4.3–5.1 inches) in diameter. Women put a 4-kg (8.82-pound) shot that is 95–110 mm (3.7–4.3 inches) in diameter.
The putter must launch the shot from within a ring 2.135 metres (7 feet) in diameter and so must gather momentum for the put by a rapid twisting movement. Shot-putters are among the largest athletes in track and field, the most massive ranging from 250 to 300 pounds (113 to 136 kg). Beginning in the 1950s, weight training became a major part of a shot-putter's training program. In that same period the O'Brien style of putting was popularized, with outstanding results. Developed by Parry O'Brien (U.S.), the style involved a 180-degree turn (rather than the usual 90-degree turn) across the ring, getting more speed and momentum into the action. O'Brien was the best exponent of the style, winning three Olympic medals (two gold) and raising the record from 17.95 metres (58 feet 10.75 inches) to 19.30 metres (63 feet 4 inches).
Some athletes have turned to a style in which the putter spins one and a half turns before releasing the shot, a technique developed by Brian Oldfield (U.S.).
The discus throw
Discus throwing is considered by many the classic event of athletics, the Greek poet Homer having made references to discus throwing in the 8th century BC. Modern male athletes throw a 2-kg (4.4-pound) platelike implement from a 2.5-metre (8.2-foot) circle. The discus is launched after the thrower, starting at the back of the circle, has completed one and a half turns. The women's discus weighs 1 kg (2.2 pounds).
Legendary among discus throwers are the feats of Al Oerter (U.S.), the first to throw over 200 feet (61 metres). He won an Olympic gold medal at the 1956 Games as a 20-year-old and at each of the following three Games as well. He also set four world records. A standout among women throwers was Faina Melnik (U.S.S.R.), who set 11 world records.
The hammer throw
The implement used in the hammer throw is not a conventional hammer but a metal ball at least 110 mm (4.3 inches) in diameter attached to a wire, the whole implement being a minimum of 1,175 mm (46.3 inches) in length and weighing a minimum of 7.2 kg (16 pounds). The handle at the end of the wire opposite from the ball is gripped by the thrower and released after three or four body turns have developed maximum centrifugal force. The throwing circle is slightly smaller than that of the discus. Women's hammer throw was introduced into international competition in the 1990s. The hammer used by women is slightly shorter and weighs a minimum of 4 kg (8.8 pounds).
American athletes of Irish birth or descent totally dominated the event from the 1890s to the 1930s and included John Flanagan, who unofficially set 17 world records and won three Olympic gold medals (1900, 1904, and 1908). After the passing of the Irish dynasty, the power shifted to the eastern Europeans. Among them was Yury Sedykh (U.S.S.R.), who won at the 1976 and 1980 Olympics and raised the record from 80.32 metres (24.5 feet) to 86.74 metres (26.4 feet).
The javelin throw
Javelin throwing involves a spearlike implement that is hurled with an over-the-shoulder motion at the end of an approach run. It is a direct descendant of spear-throwing contests, introduced in the Olympics of 708 BC. The men's javelin weighs about 800 grams (1.8 pounds) and must be at least 260 cm (8.5 feet) long. The women throw a javelin that must weigh at least 600 grams (1.3 pounds) and be at least 220 cm (7.2 feet) long. It is the only throwing event not using a circle. The javelin is not required to stick but must land point-first for a valid throw.
Throwers from Finland have historically been a force in the event. Matti Järvinen, a Finn, established 10 world records and improved the record by 6.22 metres, finally reaching 77.23 metres (253 feet 4.5 inches) in 1936. As records continued to be broken, there was less and less space within the stadium to throw the javelin safely. Terje Pedersen (Norway) broke the 300-foot (91.44-metre) barrier in 1964, and by 1984 Uwe Hohn (East Germany) had thrown a prodigious 104.80 metres (343.8 feet), a throw so great that it influenced a change in the design of the javelin to keep it within the safe confines of the field. Beginning in 1985, throwers used a javelin that, at the same weight, was designed to reduce the length of the throw by 9 to 12 metres (30 to 40 feet). The design of the women's javelin was changed after successive world records pushed close to 80 metres (262.5 feet) in the late 1980s.
Decathlon and heptathlon
Both men and women participate in multi-event competitions, the men in the 10-event decathlon and the women in the 7-event heptathlon, which superseded the earlier pentathlon. The competitions, which require a two-day schedule, are held basically at international meets and national championships. In the United States they also are scheduled in many college conference championships.
Each athlete is given points for performance in each event, with more points awarded for better marks. The athlete with the most total points wins.
Men compete in five events each day, doing consecutively the 100 metres, long jump, shot put, high jump, and 400 metres on the first day and the 110-metre hurdles, discus throw, pole vault, javelin throw, and 1,500-metre run in that order on the second day. Women do, in order, the 100-metre hurdles, high jump, shot put, and 200 metres on the first day, followed by the long jump, javelin throw, and 800 metres on the second day.
Jim Thorpe, the great all-around American athlete, won the first decathlon, taking the 1912 Olympic Games contest, and for many years it was mostly an American event. Bob Mathias (U.S.) won his first decathlon at age 17 in 1948 and repeated it four years later. Another two-time winner was Daley Thompson of England, victorious in 1980 and 1984. Notable in the heptathlon was Jackie Joyner-Kersee, a record setter and winner at the 1987 World Championships and 1988 Olympics.
spo
form of motor racing involving cars built to combine aspects of racing and touring cars. Although there are many conflicting definitions of sports cars, it is usually conceded that in normal production form they do not resemble Grand Prix (Formula One) racing machines. Whereas the latter is a single-seat design carrying spartan cockpit furnishings and utterly functional equipment throughout, the sports car is usually a two-seater, sometimes a four-seater, characterized by its nimble abilities (if not speed and power) together with general suitability for high-speed touring on ordinary roads. Unlike a Grand Prix car, it is usually series-produced, seldom handmade. Some manufacturers of Grand Prix machines, such as Ferrari and Lotus, also make sports cars. Other makes include MG, Jaguar, Aston Martin, Austin-Healey, Triumph, Porsche, Lancia, Morgan, and Chevrolet Corvette. Although not usually designed exclusively for racing, sports cars are, nevertheless, able racing machines and are often entered in competitions with others of their class. Most of the world's sports-car racing is conducted for amateur drivers by local and regional organizations. Some of the world's most famous professional races are sports-car events, however, and may even be designated as Grand Prix. (When the term Grand Prix is used in this context, it does not refer to the type of car used but rather to the race's being a major automotive event of the nation in which it is held.) The development of sports cars for racing, especially in such commercially important events as the 24-hour endurance race at Le Mans, where the reputations of participating manufacturers are very much at stake, brought about some prototype sports cars that are, in reality, little different in their power and speed potentials from Formula One machines. A world sports-car championship was awarded from 1953 to 1961. It was replaced in 1962 by a manufacturer's championship, for which grand touring and prototype cars also compete, awarded annually to the make of car that achieves the best record in a specified series of races
