A 12.1 g CD with a radius of 6.16 cm rotates with an angular speed of 31.1 rad/s. What is its kinetic energy?

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1. C=3.14 * 2 * 6.16cm = 38.68cm = 0.387m.

V = 31.1rad/s * (1/6.28)rev/rad * 0.387m/rev = 1.92m/s.

KE = 0.5mV^2 = 0.5*0.121kg*(1.92m/s) =
0.223J.

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2. CORRECTION:

Should be (1.92m/s)^2.

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