Physics of a Frisbee



What effect does the rim of a fisbee have on its flight?

The primary purpose of the rim on a frisbee is to create an airfoil with a deep curvature. When you throw a frisbee, the edge of it comes in contact with the air. As the air flows over the top of the frisbee, it speeds up and the pressure drops. This creates lift.

A frisbee without a a rim can still fly, but it won't fly as well as one with a rim. A completely flat disk will fly but the "angle of attack" becomes more of a factor as to how well it flies. A disk without a rim will be less stable in flight. You can try a simple experiment to see what role the rim plays in the flight of the frisbee. Try to fly a frisbee upside down, then compare your results to throwing a frisbee in the conventional way.

Two factors influence the flight of a Frisbee, gravity and air. Gravity acts on all objects the same way, accelerating their mass towards the center of the Earth at 10 meters/second. Once in the air, lift and angular momentum act on the Frisbee giving it a ballet-type performance. Lift is generated by the Frisbee's shaped surfaces as it passes through the air. Maintaining a positive angle of attack, the air moving over the top of the Frisbee flows faster than the air moving underneath it.

Under the Bernoulli Principle, there is then a lower air pressure on top of the Frisbee than beneath it. The difference in pressure causes the Frisbee to rise or lift. This is the same principle that allows planes to take off, fly and land. Another significant factor in the Frisbee's lift is Newton's Third Law which states that for every action there is an equal and opposite reaction. The Frisbee forces air down (action) and the air forces the Frisbee upward (reaction). The air is deflected downward by the Frisbee's tilt, or angleof attack.

Spinning the Frisbee when it is thrown, or giving it angular momentum (gyroscopic inertia), provides it with stability. Angular momentum is a property of any spinning mass. Throwing a Frisbee without any spin allows it to tumble to the ground. The momentum of the spin also gives it orientational stability, allowing the Frisbee to receive a steady lift from the air as it passes through it. The faster the Frisbee spins, the greater its stability.

Angular Momentum--A rotating body's resistance to change in its orientation and rate of rotation. This is similar to gyroscopic inertia.

Angle of Attack--The angle formed by the tilt of the flying disk and the line parallel to the ground.

Bernoulli's principle The pressure in a fluid decreases as the speed of the fluid increases.

Gravity--The force that makes objects move or tend to move toward each other.

Lift--An upward force resulting from decreasing the pressure on the top of an object by increasing the velocity of the air flowing over the top of it.

Newton's Third Law = for every action there is an equal and opposite reaction.

The information above came from a variety of sources which are sited below.  Click on the links to learn more about the physics and history of a Frisbee.

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