On an Amusement Park Ride, Passengers Are Seated in a Horizontal

Multiple Choice

On an amusement park ride, passengers are seated in a horizontal circle of radius 7.5 m. The seats begin from rest and are uniformly accelerated for 21 seconds to a maximum rotational speed of 1.4 rad/s.
-What is the instantaneous tangential speed of the passengers 15 s after the acceleration begins?

A) 0.067 m/s
B) 0.50 m/s
C) 1.4 m/s
D) 7.5 m/s
E) 11 m/s