The Frisbee page 1
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Introduction

If you have ever been to the park or the beach, you've probably have seen one of these plastic discs flying through the air. I'm not talking about a UFO, I'm talking about the Frisbee, more generically known as the flying disc. The Frisbee has fascinated us for decades and has become as common to us as the baseball or the football. The Frisbee has even developed sports of its own. Some Frisbee games, like Frisbee Golf (Folf) and Frisbee Baseball, imitate existing sports. Others, such as Ultimate Frisbee and Guts, were inspired by the Frisbee itself. Frisbee catching has even become a popular sport for dogs. What is it which so fascinates us with this plastic flying disc? Perhaps we are amazed by the fact that such a simple object can glide effortlessly through the air. Maybe we are soothed by its graceful fight patterns, or maybe Frisbees are just fun to throw. Let's take a closer look at the flying toy that has become so popular in today's society.

History

Frisbie Frisbee's over the years have pretty much remained the same size and shape. The original Frisbee's were actually pie tins back in the late 1800's. College students in those days, would toss the pie back and forth to each other. Then it was common for pie companies to engraved their name in each of the pie tins. One pie company, the Frisbie Pie Company, owned by William Frisbie, produced a pie tin which was popular with Yale students. The Yale students started calling these flying pie tins by the name engraved on them, hence the name Frisbie (now Frisbee) became the popular term for one of today's most recognized flying toy.

Dynamics

What makes a Frisbee fly? Just like a bird's wing or the wing of an airplane shape plays a large part in influencing the flying ability of the Frisbee. As mentioned before the design of the Frisbee has not changed a whole lot from its beginnings as a pie tin. It is still light weight, circular, fairly flat, and the edges of the Frisbee are either sloped or rounded.

Frisbee
If we take a look at the Frisbee from the side we can see that the rounded edges of the Frisbee looks similar to the front edge of a aircraft wing. We know that the curved upper surface of the wing is what generates lift. The same principle applies to the Frisbee. As air passes over the curved upper surface of the Frisbee it speeds-up, creating a low pressure region on top of the Frisbee. Below the Frisbee air passes more slowly, creating a high pressure region. The difference in pressure gives the Frisbee lift.

Frisbee


Even though the shape of the Frisbee may generate lift, lift is not the only requirement for flight. Try throwing a Frisbee without spinning it. Notice how it wobbles and tumbles. The shape of the Frisbee may be generating lift, but the Frisbee is unstable. It cannot stay upright and eventually stalls. All flying things must have something which makes them stable during flight; airplanes and birds have tails, rockets have fins. For a Frisbee it is the spinning motion generated from the Frisbee throw, which stabilizes the Frisbee as it flies.

*illustration of angular momentum of a Frisbee*

In order to understand why a spinning makes a Frisbee stable in flight, we must first understand the concept in physics known as angular momentum. All things which spin are said to posses angular momentum. Angular momentum can be represented by a magnitude and a direction. The magnitude of angular momentum is determined approximately by the mass of the spinning object and the rate at which the object spins. The direction is determined by the axis of spin. The law of angular momentum states that the angular momentum of an object will remain constant unless acted upon by an external force. This means once something starts spinning, it takes an angular force, or torque, to alter it's axis of rotation. Take the gyroscope for example. Start a gyroscope spinning, Then grab the ends of the gyroscope with your hands. Now try to turn it upside-down. You'll notice it takes effort to do this. The same phenomenon which makes a gyroscope difficult to flip over is what allows Frisbees to fly steadily through the air.

*illustration of flipping a gyroscope, show angular momentum and torque*

The stabilizing effects of spinning can be seen in other things as well. Take for instants, the top. A non-spinning top will always fall on its side. Only when the top spins is it able to dance on its tip. A bicycle also benefits from angular momentum. When at a stop sign it is difficult for a bicyclist to balance on the two wheels of a bicycle. When the bicyclist starts moving the pedals on the bicycle, making the wheels spin, the angular momentum of the wheels makes it much easier for him/her to balance.

*illustration of the angular momentum of a top and a bicycle*

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