Problem 1.192

A small ball is suspended from a point \(O\) by a light thread of length \(l\). Then the ball is drawn aside so that the thread deviates through an angle \(\theta\) from the vertical and set in motion in a horizontal direction at right angles to the vertical plane in which the thread is located. What is the initial velocity that has to be imparted to the ball so that it could deviate through the maximum angle \(\pi / 2\) in the process of motion?