Answer
$420\ rev$
Work Step by Step
Initial angular acceleration speed $\omega_i=1200\ rev/s$
Final angular acceleration speed $\omega_f=3000\ rev/s$
Angular acceleration $\alpha =9000\ rev/min^2$
From rotational kinematics equation, we have:
$\omega_f^2-\omega_i^2 = 2\alpha\theta$
$(3000\ rev/min)^2 - (1200\ rev/min)^2 = 2 (9000\ rev/min^2)\theta$
$7560000 (rev/min)^2 = 2 (9000\ rev/min^2)\theta$
$\theta = 420\ rev$
