Null

!((Clear[Ex, Ey, x, Vx, y, Vy]; )n
  x[0] = 0. ; Vx[0] = 3 10^6; y[0] = 0. ; Vy[0] = 0. ; n
  Delta = 1.0/10^9; Steps = 10; n
  q = 1.6/10^19; m = 9.1/10^31; n
  Ex = 0. ; Ey = 1000. ; n
  Do[Fx = q Ex; Fy = q Ey; Vx[n + 1] = Vx[n] + (Fx Delta)/m; 
    Vy[n + 1] = Vy[n] + (Fy Delta)/m; x[n + 1] = x[n] + Vx[n + 1] Delta; 
    y[n + 1] = y[n] + Vy[n + 1] Delta, {n, 0, Steps}])

data=Table[{x[n],y[n]},{n,0,Steps}];
plot1=ListPlot[data,AxesLabel[Rule]{"x","y"}];

!((Clear[Ex, Ey, x, Vx, y, Vy]; )n
  x[0] = 0. ; Vx[0] = 3 10^6; y[0] = 0. ; Vy[0] = 0. ; n
  Delta = 1.0/10^9; Steps = 17; n
  q = 1.6/10^19; m = 9.1/10^31; n
  Ex = 0. ; Ey = 1000. ; n
  Do[If[n [LessEqual] 10, Fx = q Ex; Fy = q Ey, Fx = 0. ; Fy = 0. ]; 
    Vx[n + 1] = Vx[n] + (Fx Delta)/m; 
    Vy[n + 1] = Vy[n] + (Fy Delta)/m; x[n + 1] = x[n] + Vx[n + 1] Delta; 
    y[n + 1] = y[n] + Vy[n + 1] Delta, {n, 0, Steps}])

data=Table[{x[n],y[n]},{n,0,Steps}];
plot2=ListPlot[data,AxesLabel[Rule]{"x","y"}];

!((Clear[Ex, Ey, x, Vx, y, Vy]; )n
  Eo = 1000. ; DeltaX = 0.03/10; Steps = 10. ; n
  Do[Ey[n] = Eo ((1 - n/Steps)); x[n] = n DeltaX, {n, 0, Steps}]n
  (FieldData = Table[{x[n], Ey[n]}, {n, 0, Steps}]; )n
  (ListPlot[FieldData, AxesLabel [Rule] {"<x>", "<Ey>"}]; ))

!((Clear[Ex, Ey, x, Vx, y, Vy]; )n
  x[0] = 0. ; Vx[0] = 3 10^6; y[0] = 0. ; Vy[0] = 0. ; n
  Delta = 1.0/10^9; Steps = 10; n
  q = 1.6/10^19; m = 9.1/10^31; Eo = 1000. ; n
  Do[Ey[n] = Eo ((1 - n/Steps)); Fy = q Ey[n]; Vx[n + 1] = Vx[n]; 
    Vy[n + 1] = Vy[n] + (Fy Delta)/m; x[n + 1] = x[n] + Vx[n + 1] Delta; 
    y[n + 1] = y[n] + Vy[n + 1] Delta, {n, 0, Steps}])

data=Table[{x[n],y[n]},{n,0,Steps}];
plot3=ListPlot[data,AxesLabel[Rule]{"x","y"},PlotJoined[Rule]True];