At time           peak is at             equation is
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                                                 -x^2
      t = 0 s             x = 0 m           y = e 

                                                 -(x - 3 m)^2
      t = 1 s             x = 3 m           y = e

                                                 -(x - 3 m)^2
      t = 2 s             x = 6 m           y = e

                                                 -(x - 3 m)^2
      t = 3 s             x = 9 m           y = e

                                                 -(x - 3 m)^2
      t = 4 s             x = 12 m          y = e

         and in general

                                                 -(x - [3 m/s*T] )^2
      t = T s             x = (3 m/s) * T   y = e
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