Physics of the Frisbee
What makes Frisbees fly so perfectly? According to a paper linked to MIT’s website (http://web.mit.edu/womens-ult/www/smite/frisbee_physics.pdf), the two main concepts are the Bernoulli principle (for lift) and angular momentum (for stability). Apparently, a Frisbee’s flight can be compared to that of an airplane wing. As we learned in Physics B, the Bernoulli Principle states that fluids flowing with a higher velocity have lower pressures. Mathematically: v12/2 + p1/row +gh1 = v22/2 + p2/row +gh1 (v is velocity, p is pressure, h is height of fluid, g is acceleration due to gravity and row is density of the fluid). A Frisbee’s curved shape ensures that air passing up and over the Frisbee must travel further (and therefore faster) than the air that travels beneath it. Hence, lift is provided by lower pressure above the Frisbee than below it. As for stability, greater spin- greater angular velocity- is desired when throwing a Frisbee because more spin means more angular momentum. (Angular momentum is the cross product of moment of inertia and angular velocity). Just as linear momentum ensures that an object in linear motion will tend to stay in motion unless acted upon by an outside force, greater angular momentum ensures that the disc will tend to rotate in the same plane, which reduces wobbling and leaning during flight.
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