ScienceIQ.com

Large Asteroid Zooms Safely Past Earth

A mountain-sized asteroid made its closest approach to Earth at 9:35 a.m. Eastern Time on Wednesday, Sept. 29, 2004. Although asteroid 4179 Toutatis came no closer than four times the distance between Earth and the Moon (approximately 1.5 million kilometers or 961,000 miles), this is the closest approach of any known asteroid of comparable size ...

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LargeAsteroidZoomsPastEarth
Medicine

The Neurological Complications Of Lyme Disease

Lyme disease is caused by a bacterial organism that is transmitted to humans via the bite of an infected tick. Most people bitten by an infected tick develop a characteristic skin rash around the area ... Continue reading

LymeDisease
Mathematics

How To Calculate The Circumference Of A Circle

A circle is what you get if you take a straight line and bend it around so that its ends touch. You can demonstrate this by taking a piece of stiff wire and doing just that: bring the ends of the wire ... Continue reading

CircumferenceOfACircle
Biology

Butterflies In Your Brain

The idea behind chaos theory is that complex systems have an inherent element of unpredictability. The human brain certainly qualifies as a complex system. It is also a chaotic system. It does not ... Continue reading

ButterfliesInYourBrain
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.