A 5.0-g CD with a radius of 6.0 cm rotates with an angular speed of 20 rad/s. What is its kinetic energy?
C = pi*D = 3.14 * 2*6 = 37.68 cm = 0.377 m. = Circumference.
V = 20rad/s * 0.377m/6.28rad=1.20 m/s.
KE = 0.5m*V^2 = 0.0025*(1.20)^2=0.0036
Joules.