Answer
a) $\omega$ is zero
b) $\alpha$ is negative
Work Step by Step
Because the pendulum is at the end of its arc, it is no longer traveling away from the middle of the arc and has not begun swinging back, so its angular velocity $\omega$ is zero. At this point, the ball is accelerating back towards the center of its arc to return to equilibrium, this is to the left in the clockwise direction, so angular acceleration $\alpha$ is negative.
