Physics problem, how to do, thanks?

it's linear velocity is 2 m / 2 s = 1 m/s

circumference is πd = 2πr = 2π m

time to travel one circumference is 2π m / 1 m/s = 2π sec

1 circumference (or revolution) is 2π radians
(1 circum. / 2π s ) x (2π rad / circum.) = 1 rad/s = ω


alternate:
An arc of a circle with the same length as the radius of that circle subtends an angle of 1 radian.

in 1 sec, it moves 1 m along an arc of radius 1 m, therefore that is an arc of 1 rad. therefore 1 rad/s