Question Detail
Question
A solid circular disk of radius 0.6 m and mass 90 kg is rotating at 460 rev/min. What force, applied tangentially to the edge, will cause the disk to stop in 20 s?
Correct Answer
Option D is the correct answer.
Detailed Explanation
Convert 460 rev/min to rad/s: ω = 48.17 rad/s. Angular deceleration α = −48.17/20 = −2.41 rad/s². Moment of inertia I = (1/2)mr² = 16.2 kg·m². Torque τ = Iα = −39.1 N·m. Force F = τ/r = −39.1/0.6 ≈ −65 N.
Hint
Use τ = Iα and F = τ/r.