The ball is at the height 11 meters, when


    1 + 25t - 5t^2 = 11   meters.


Solve this quadratic equation to find "t".


    5t^2 - 25t + 10 = 0

      t^2 - 5t + 2 = 0

       =  = 


       =  = 0.44 seconds (approximately),   and

       =  = 4.56 seconds (approximately).



   


    Plot y =  (red) and y = 11 (green)



Time moment   corresponds to the ball moving up.

Time moment   corresponds to the ball falling down.