When the play button is pressed, a CD accelerates uniformly from rest to 420 rev/min in 2.7 revolutions. If the CD has a radius of 6 cm, and a mass of 17 g, what is the torque exerted on it?
2 Answers
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We determine α (angular acceleration) from
ω^2 = ωo^2 + 2 α θ so ωo =0
therefore α = ω^2/(2θ) = (420*2π/60)^2/(2*2.7*2π) = 57.0 rad/s^2
Now I = 1/2*M*r^2 = 1/2*0.017kg*(0.060m)^2 = 3.06x10^-5 kg-m^2
Now torque τ = I*α = 3.06x10^-5kg-m^2*57.0 rad/s^2 = 1.74x10^-3 N-m
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