Initial angular speed, ω0=360 rpm=360×602π rad/s=12π rad/s.
Final angular speed, ω=1200 rpm=1200×602π rad/s=40π rad/s.
Time, t=14 s.
Using the kinematic equation for uniform rotational acceleration, ω=ω0+αt:
α=tω−ω0
α=1440π−12π
α=1428π=2π rad/s2.