A boy throws a ball with speed u in a well of depth 14 m as shown. On bounce with bottom of the well the speed of the ball gets halved. What should be the minimum value of u/10 (in m/s) such that ball may be able to reach his hand again? It is given that his hands are at 1 m height from top of the well while throwing and catching.  $(g=10m/s^2)$