A uniform disk of rotational inertia \(I\) is initially at rest and driven by a motor that delivers a constant mechanical power \(P_0\). The rotation of the disk is opposed by a viscous damping torque of magnitude \(\tau = b\omega\), where \(b\) is a positive constant and \(\omega\) is the instantaneous angular speed. The angular speed of the disk as a function of time \(t\) is given by \(\omega(t) = \sqrt{\dfrac{P_0}{b}\left(1 - e^{-2bt/I}\right)}\). For a fixed time \(t > 0\), which of the following expressions represents the angular speed of the disk in the limit as the damping coefficient \(b\) approaches zero?