Using the equation of rotational kinematics θ=ω0t+21αt2.
Since the wheel is initially at rest, ω0=0.
Angle rotated in the first 2 s:
θ1=21α(2)2=2α
Angle rotated in the first 4 s:
θtotal=21α(4)2=8α
Angle rotated in the next 2 s:
θ2=θtotal−θ1=8α−2α=6α
The ratio is:
θ1θ2=2α6α=3
Answer: 3