Question

A 110 g Frisbee is 18 cm in diameter and has half its mass spread uniformly in the disk and the other half concentrated in the rim.

a.)

What is the Frisbee's rotational inertia?

Express your answer using two significant figures.

b.)

With a quarter-turn flick of the wrist, a student sets the Frisbee rotating at 730 rpm . What is the magnitude of the torque, assumed constant, that the student applies?

Express your answer using two significant figures.

Answer 1

The rotational inertia will be sum of the inertia of the disk part and the ring part which is at the rim. Use work energy theorem to find the required magnitude of torque as shown below

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