Angular Acceleration

Question

During the time a compact disk (CD) accelerates from rest to a constant rotational speed of 385rpm, it rotates through an angular displacement of 0.450rev. What is the angular acceleration of the CD in rad/s²

Answer 1

Angle of revolution ω² = 2εφ; ε = ω²/(2φ); ω = 385rpm = 365·2π/60 rad/s = 48.32 rad/s; φ = 450·2π = 2827.43 rad; ε = 48.32²/(2·2827.32) = 0.413 rad/s²