ScienceIQ.com

Who was Typhoid Mary?

Mary Mallon lived in New York about 100 years ago, and worked as a cook. It seemed that every family she worked for suffered an outbreak of typhoid fever! The Dept. of Public Health found that she harbored the bacteria salmonella typhi, which causes typhoid fever. Even though there were no antibiotics in those days, doctors did know how to culture ...

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WhowasTyphoidMary
Engineering

The Right Stuff for Super Spaceships

Revolutions in technology - like the Industrial Revolution that replaced horses with cars - can make what seems impossible today commonplace tomorrow. ... Continue reading

SuperSpaceships
Geology

What are Hoodoos?

Hoodoos or Goblins are one of the most spectacular displays of erosion. They are geological formations, rocks protruding upwards from the bedrock like some mythical beings, conveying the story of ... Continue reading

WhatareHoodoos
Biology

Why Tree Twig Twine Twists Tongues

Even though we call it a 'tongue twister,' it isn't really your tongue that has a hard time saying 'sixth sick sheik's sixth sheep's sick.' It's not all that rare for people to make mispronunciations ... Continue reading

TreeTwigTwineTwists
Biology

An Invasion of Infiltrators

Why might a species be invasive in one country but not a big problem in its native land? As an example, consider a plant that is a major weed in the U.S. but in its native land it may be a minor pest. ... Continue reading

Infiltrators

Get the Point?

DiscusJavelinThe discus and javelin first appeared in ancient game competitions in 708 B.C. Javelin events included both target throwing and distance throwing using a sling. By 1780, the javelin was adopted as an event by the Scandinavians, and the current one-handed throwing style while running was adopted at this time. In 1953, a hollow javelin was developed in the United States by Franklin 'Bud' Held who also set a new world record. Since the javelin had a standard weight, the surface area was increased which augmented the javelin's flight capability and caused it to land horizontally. In 1966, the javelin was thrown over 100 meters (328 feet) by an athlete using a discus style turn before the throw. This throwing style was judged unsafe and thereafter banned by the International Amateur Athletic Federation (IAAF). The 100-meter mark was broken again in 1984. Subsequently, the IAAF adopted new rules to ensure shorter flight times and sport safety.

The modern javelin is designed with the center of pressure located behind the center of gravity. This generates a nose down pitching moment (the tendency to produce motion about a point or axis), which reduces the javelin's flight time. Although the center of pressure's location varies during the javelin's flight, it always remains behind the center of gravity. As a result, the nose of the javelin pitches down. This nose down orientation also guarantees that the javelin lands point first. A point first landing ensures a safer event. In addition, since the javelin can no longer slide across the ground, the distance can be measured with greater accuracy.

During flight, the javelin also spins about its longitudinal axis. At a rate as high as 25 revolutions per second, the spin stabilizes the javelin in flight. The javelin also experiences oscillation down its length during flight. Oscillation is detrimental to the flight and needs to be minimized by the thrower or by the materials used in the javelin. Modern javelins are made from steel, aluminum or aluminum alloy. Novice throwers use a less stiff javelin (which is more forgiving in training). As skill is developed, a stiffer javelin is used (straighter flight). The steel javelins are the stiffest and have less vibration than the aluminum models, while aluminum offers flexibility and may be easier to throw.