why does stone tied to a strong string and roated, fly off tangentially when released

When the stone tied to the string is rotated it is said to be in uniform circular motion.Our hand is holding the string and is providing the centripetal force to it (force which always acts towards the centre of a circular path).Here the tension force in the string provides the centripetal force.The direction of velocity of the stone is tangential to the circular path it is following.When the string is released the centripetal force stops acting and so the body is unable to maintain its state of uniform circular motion any more.As its velocity (when it was moving) is tangential to the circular path,when it's released it moves tangentially.