The boy rotates a stone on a rope of 1.2 meters in length. Determine the period of revolution of the stone

The boy rotates a stone on a rope of 1.2 meters in length. Determine the period of revolution of the stone if its average speed is 18 km / h.

R = 1.2 m.
V = 18 km / h = 5 m / s.
T -?
The period of rotation T is the time of one complete revolution of the stone. With one revolution, the stone travels a path S equal to the circumference: S = 2 * P * R, where P is the number pi, R is the radius of the circle along which the stone moves.
T = S / V = 2 * P * R / V.
T = 2 * 3.14 * 1.2 m / 5 m / s = 1.5 s.
Answer: the period of rotation of the stone is T = 1.5 s.