A flywheel, starting from rest, has its angular velocity varying with time as follows:
0 ≤ t ≤ 3 s: ω=4t (rad s−1)
3 s < t ≤ 6 s: ω=12 (rad s−1)
6 s < t ≤ 9 s: ω=12−2(t−6) (rad s−1)
a. (i) Calculate the total angular displacement from t=0 to t=9s.
b. (ii) Find the instantaneous angular acceleration at t=1s and at t=7s.