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AP Physics C: Mechanics
5.6 Newton’s Second Law in Rotational Form
5.1 Rotational Kinematics
AdvancedMCQMathematicalConceptual19k
A perspective diagram showing a circular flywheel viewed at an angle as a thin shaded gray ellipse centered on a horizontal axle. The axle is represented by a solid horizontal line passing through the center of the ellipse. A curved arrow labeled \(\omega_0\) loops over the top edge of the ellipse pointing in the direction of rotation. Adjacent to the upper rim of the ellipse is a small shaded rectangular block labeled Brake. A small straight arrow labeled \(\tau(t)\) points along the rim opposite to the direction of \(\omega_0\). No other labels, lines, text, or axes appear.
Flywheel with initial angular speed \(\omega_0\) and opposing braking torque \(\tau(t)\).
A flywheel with rotational inertia \(I\) is mounted on a fixed frictionless axle and rotates freely with an initial angular speed \(\omega_0\). At time \(t = 0\), a magnetic brake is engaged, exerting a retarding torque of magnitude \(\tau(t) = \tau_0 e^{-t/T}\) that opposes the rotation, where \(\tau_0\) and \(T\) are positive constants satisfying \(\tau_0 T < I \omega_0\). Which of the following statements correctly describes the angular speed \(\omega(t)\) and total angular displacement \(\Delta\theta(t)\) of the flywheel in the limit as \(t \to \infty\)?

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