# Thoroughly confused by NDSolve

Posted 9 years ago
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 Hi all, I am new to using Mathematica and slowly getting the hang of things but I still find the approach confusing at times.So having read up on the tutorials for using NDSolve, and testing it out on a few toy equations that I can solve by hand, I tried setting it up to solve a real problem.  (Electron motion in a laser field).  NDSolve appears to run and provides me with a "solution" of InterpolatingFunctions but when I come to evaluate them they do not evaluate, (see code below).  What am I doing wrong here? c0 = 1; \[Omega] = 1; vg = 1; vp = 1; \[Sigma] = 1; \[Rho] = 1; Subscript[A, 0] = 1; q = 1; m = 1;y = 0;A[x_, z_, t_] :=   Subscript[A, 0]    Exp[-(z - vg t)/\[Sigma]^2] Exp[(-x^2 - y^2)/\[Rho]^2] Exp[    I \[Omega] (z/vg - t)];s = NDSolve[{D[x[t], {t, 2}] == q/m D[A[x[t], z[t], t], t],    D[z[t], {t, 2}] == -(q/m) D[x[t], t] A[x[t], z[t], t], x'[0] == 0,    z'[0] == 0, x[0] == 0, z[0] == 0}, {x[t], z[t]}, {t, 0, 10}]Plot[Evaluate[{x[t], z[t]} /. s], {t, 0, 10}, PlotRange -> All]Evaluate[{x[1], z[1]} /. s]This simply refuses to evaulate and gives me an empty graph and {{x[1], z[1]}}What am I missing?