A horizontal pipe 100m in length with a diameter of 500mm and a steady velocity of 0.

 A horizontal pipe 100m in length with a diameter of 500mm and  a steady velocity of 0.5 m/s is suddenly subjected to a new piezometric head differential of 20m when the downstream value suddenly opens and its coefficient changes to k= 0.2 .Assuming a friction factor of f= 0.02, determine the final steady -state velocity and the time when the actual velocity is 75% of the final value.