Answer: 0.47 rad/sec 
Explanation: 
By definition, the angular velocity is the rate of change of the angle traveled with time, so we can state the following: 
ω = ∆θ/ ∆t 
Now, we are told that in 13.3 sec, the ball completes one revolution around the circle, which means that, by definition of angle, it has rotated 2 π rad (an arc of 2πr over the radius r), so we can find ω as follows: 
ω = 2 π / 13.3 rad/sec = 0.47 rad/sec