Final answer:
To find the time when the motor reverses direction, set the angular velocity equation equal to zero and solve for t.
Step-by-step explanation:
To find the time when the motor reverses direction, we need to set the angular velocity equation equal to zero.
Given: ω = 20 - 0.5t² where t is in seconds.
Setting ω equal to zero: 0 = 20 - 0.5t²
Solving for t:
t² = 40
t = ±√40
Since time cannot be negative, the motor reverses direction when t = √40 seconds.