Question

A wheel starts from rest and rotates about its axis with constant angular acceleration. After 8.7 s have elapsed, it has rotated through an angle of 20 radians. I found that the angular velocity at 8.7 s is 4.60 rad/s.
What is the angular acceleration of the wheel?
What is the centripetal acceleration of a point on the wheel a distance r = 0.25 m from the axis at t = 8.7 s?