Frisbee

Frisbees are disc-shaped objects, which are generally plastic and roughly 20 to 25 centimeters (8-10inches) in diameter, with a lip. The shape of the disc, an airfoil in cross-section, allows it to fly by generating lift as it moves through the air while rotating. The name Frisbee is a registered trademark of the Wham-O toy company, but is often used generically to describe all flying discs. 
Flying discs are thrown and caught for recreation, and as part of many different flying disc games. A wide range of flying disc variants are available commercially. Disc golf discs are usually smaller but denser and are tailored for particular flight profiles to increase/decrease stability and distance. Disc dog sports use relatively slow flying discs made of more pliable material to better resist a dog's bite and prevent injury to the dog. Ring shaped discs are also available which typically fly significantly farther than any traditional flying disc. There are illuminated discs meant for night time play that use phosphorescent plastic, or battery powered light emitting diodes. There are also discs that whistle when they reach a certain velocity in flight.
==History==
The Frisbie Pie Company (1871–1958) of Bridgeport, Connecticut, made pies that were sold to many New England colleges. Hungry college students soon discovered that the empty pie tins could be tossed and caught, providing endless hours of sport. Many colleges have claimed to be the home of "he who was first to fling." A Dartmouth College ex has argued, tongue-in-cheek,that in 1920, an undergraduate named Elihu Frisbie grabbed a collection plate from the chapel and flung it out into the campus, thereby becoming the true inventor of the Frisbee. That tale is dubious, as the "Frisbie's Pies" origin is well-documented. Walter Frederick Morrison claims that it was a popcorn can lid that he tossed with his girlfriend (and later wife) Lu at a 1937 Thanksgiving Day gathering in Los Angeles that inspired his interest in developing a commercially-produced flying disc. In 1946 he sketched out plans for a disc he called the Whirlo-Way, which, co-developed and financed by Warren Franscioni and Erich Drafahl in 1948, became the very first commercially produced plastic flying disc, marketed under the name Pipco Flyin-Saucer. Morrison had just returned to the US after World War II, where he had been a prisoner of war. His partnership with Franscioni, who was also a war veteran, ended in 1950, before their product had achieved any real success.
The Ivy League fad of spinning pie tins with shouts of "frisbie" which Morrison witnessed in Harvard Yard in 1957, and which inspired him to trademark the name phonetically as "Frisbee," started more than ten years before at Yale. I know, because I started the fad in the courtyard of the Law School the day after I registered for my third year of law in mid-October, 1946. The pasttime became a fad there within a few days, and spread to the undergrads within a few weeks. They named it for the pie tins they used, having "Frisbie" pressed into the tin. (Frisbie pies were not sold in Cambridge or Princeton, only across southern Connecticut and Rhode Island.) My article describing its origins was published in the Yale Alumni Magazine 50 years later, in the Feb.-Mar.1996 issue, pp. 47-49. Archivist Judith Ann Schiff's 2007 article implied that I claimed to have been the first to spin a pie tin at Yale; but I made no such claim -- how would I know? I only know I started the post-war fad which created a ready market for Wham-O's plastic disc.
In 1955, Morrison produced a new plastic flying disc called the Pluto Platter, to cash in on the growing popularity of UFOs with the American public. The Pluto Platter became the design basis for later flying discs. In 1957, Wham-O began production of more discs (then still marketed as Pluto Platters). The next year, Morrison was awarded US Design Patent 183,626 for his flying disc.
In 1957,Wham-O co-founder Richard Knerr, decided to stimulate sales by giving the discs the additional brand name "Frisbee" (pronounced the same as "Frisbie"), after hearing that East Coast college students were calling the Pluto Platter by that name. The man who was behind the Frisbee's phenomenal success however was "Steady" Ed Headrick, hired in 1964 as Wham-O's new General Manager and Vice President in charge of marketing. Headrick soon redesigned the Pluto Platter by reworking the rim thickness, and top design, creating a more controllable disc that could be thrown accurately. 
Sales soared for the toy, which was marketed as a new sport. In 1964, the first "professional" model went on sale. Headrick patented the new design as the Frisbee patent, highlighting the “Rings of Headrick” and marketed and pushed the professional model Frisbee and "Frisbee" as a sport. (US Patent 3,359,678).
Headrick, commonly known as the "Father of Disc Sports", later founded "The International Frisbee Association (IFA)" and began establishing standards for various sports using the Frisbee such as Distance, Freestyle and Guts. Upon his death, Headrick was cremated, and his ashes, in accordance with his final requests, were molded into memorial Frisbees and given to family and close friends.
==Physics==
Lift is generated in primarily the same way as a traditional asymmetric airfoil, that is, by accelerating upper airflow such that a pressure difference gives rise to a lifting force. Small ridges near the leading edge act as turbulators, reducing flow separation by forcing the airflow to become turbulent after it passes over the ridges. 
The rotating flying disc has a vertical angular momentum vector, stabilizing its attitude gyroscopically. Depending on the cross-sectional shape of the airfoil, the amount of lift generated by the front and back parts of the disc may be unequal. If the disc were not spinning, this would tend to make it pitch. When the disc is spinning, however, such a torque would cause it to precess about the roll axis, causing its trajectory to curve to the left or the right. Most discs are designed to be aerodynamically stable, so that this roll is self-correcting for a fairly broad range of velocities and rates of spin. However, many disc golf discs are intentionally designed to be unstable. Higher rates of spin lead to better stability, and for a given rate of spin, there is generally a range of velocities that are stable.
Even a slight deformation in a disc (called a "Taco," as extreme cases look like a (taco shell) can cause adverse affects when throwing long range. It can be observed by holding the disc horizontally at eye level and looking at the rim while slowly rotating the disc.
==Video Clip==
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