A strong board of length 2l = 4 m can rotate freely around a horizontal axis passing through its middle. One end of the board is attached to the floor by a rigid spring (the height of the support is much less than the length of the board). At this end lies a ball of mass m = 10 kg. A boy of mass M = 30 kg jumps to the other end from a height h = 1.5 m (figure). When landing, there is a push, the board turns, the ball is thrown up and does not return to the board. Determine to what height x the stretched spring will throw the boy

Answer. Format gif