the 10 seconds barrier was the time for world-class sprinters in the 100 -meter race . the first athlete to do so was jim Hines in 1968 . it has been done many times since but no one has yet gone below 9 seconds , what is the speed in km/hr of someone who can run 100 meters in 10 seconds ?show your working
Answers
The 10-second barrier is the physical and psychological barrier of completing the 100 metres sprint in under ten seconds. The achievement is traditionally regarded as the hallmark of a world-class male sprinter. Its significance has become less important since the late 1990s, as an increasing number of runners have surpassed the ten seconds mark.[1] The current men’s world record holder is Usain Bolt, who ran a 9.58 at the 2009 IAAF World Championship competition.
History
See also: Men's 100 metres world record progression
For sprints, World Athletics maintains that world records and other recognised performances require: a wind assistance of not more than two metres per second (7.2 kilometres per hour (4.5 mph)) in the direction of travel; fully automatic timing (FAT) to one hundredth of a second; and no use of performance-enhancing substances.[5] Wind gauge malfunctions or infractions may invalidate a sprinter's time.[6]
Hand timing
Prior to 1977, FAT was not required for IAAF official timings.[2] Times were recorded manually to one tenth of a second; three official timers with stopwatches noted when the starting gun flashed and when the runner crossed the finish line, and their median recorded time was the official mark. Some races also had an unofficial FAT, or semi-automatic time, often in conjunction with photo finish equipment. The first person timed at under ten seconds was Bob Hayes, who ran 9.9 s in April 1963 at the Mt. SAC Relays, but with a tailwind of 11 mph (4.9 m/s).[3][4] Hayes clocked another illegal 9.9 s (wind 5.3 m/s (12 mph)) in the semi-final of the 1964 Olympic 100 m, with the first sub-10 FAT of 9.91 s.[5] In the final, Hayes' official tenths time of 10.0 s was calculated by rounding down the FAT of 10.06 s; the backup hand-timers recorded 9.8, 9.9, and 9.9, which would have given 9.9 s as the official time if the FAT had malfunctioned.[2]At the 1968 USA Outdoor Track and Field Championships at Charles C. Hughes Stadium in Sacramento, California, United States, three men ran legal hand-timed 9.9 seconds: Jim Hines first and Ronnie Ray Smith second in the first semi-final, and Charlie Greene first in the second semi-final.[2][6] This was dubbed the "Night of Speed", and all three were recognised as world records by the IAAF.[2] The IAAF lists their FATs as: Hines 10.03, Smith 10.14 and Greene 10.10;[2] although Time magazine reported at the time that "an automatic Bulova Accutron Phototimer confirmed that all three had indeed broken [10.0s]".[7] Hines also had a wind-assisted 9.8 s in the heats.[7] Hines went on to win the 1968 Olympic 100m in 9.9 s, rounded down from his FAT of 9.95, making it the first non-wind-assisted electronic sub-10-second performance.[2] By 1976, six other men had equalled the 9.9 s hand-timed record, though none of their performances had an FAT mark.[2]