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The Importance of Cave and Karst Systems

Cave and karst systems are important for two major reasons. First, the overwhelming majority of the nation's freshwater resources is groundwater. About 25% of the groundwater is located in cave and karst regions. The protection and management of these vital water resources are critical to public health and to sustainable economic development. As ...

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ImportanceofCaveaKarstSystems
Physics

Quarks

Quarks are the most fundamental particles that we know of. Both protons and neutrons are made of quarks. We know quarks exist; we have experimental proof. However nobody has been able to isolate them; ... Continue reading

Quarks
Engineering

Pass the Basalt

Advanced composite materials technology is a field that is growing both quickly and steadily. That new fiber materials and applications will be developed is the proverbial 'no brainer'. However, ... Continue reading

PasstheBasalt
Engineering

Searing Heat, Little Package

Engineers have created a miniature hotplate that can reach temperatures above 1100C (2012F), self-contained within a 'laboratory' no bigger than a child's shoe. The micro-hotplates are only a few ... Continue reading

SearingHeatLittlePackage
Astronomy

Starburst, No, Not The Candy

A starburst galaxy is a galaxy experiencing a period of intense star forming activity. Although this activity may last for ten million years or more, that is like a month in the life of a ten billion ... Continue reading

StarburstAstro

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.