I want to be able to add in a second object into the same animation frame.

Questions
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1

I want to be able to add a second pendulum with independent initial conditions, but at the same time I want it to run on the same frame so I can compare the two systems. Everything that I have tried so far hasn’t worked for me. Here is my code, I will attach the file as well.
Needs[“VariationalMethods`”]

Clear[s1, s2, [Phi]1, [Phi]2, t, g, m1, m2];
variables = {[Phi]1[t], [Phi]2[t]};
r1 = s1 {Sin[[Phi]1[t]], -Cos[[Phi]1[t]]};
r2 = r1 + s2 {Sin[[Phi]2[t]], -Cos[[Phi]2[t]]};

lagrangian =
m1/2 D[r1, t].D[r1, t] + m2/2 D[r2, t].D[r2, t] -
g {0, 1}.(m1 r1 + m2 r2);
eqs = EulerEquations[lagrangian, variables, t];

s1 = 1;
s2 = 1;
m1 = 1;
m2 = 1;
g = 9.81;
tMax = 30;
initial = {[Phi]1[0] == Pi/2, [Phi]2[0] == Pi/2, [Phi]1’[0] ==
Pi/2, [Phi]2’[0] == 0};
sol = First[NDSolve[Join[eqs, initial], variables, {t, 0, tMax}]];
nFrames = 1000;
frames = Table[
Graphics[{Gray, Thick, Line[{{0, 0}, r1, r2}], Darker[Black],
Disk[{0, 0}, .1], Darker[Black], Disk[r1, m1/10],
Disk[r2, m2/10]} /. sol,
PlotRange → {{-2.5, 2.5}, {-2.5, 2.5}},
Background → Lighter[White]], {t, tMax/nFrames, tMax,
tMax/nFrames}];
ListAnimate[frames]

DoublePendulum.nb (698 KB)

2

You can animate two plots side-by-side for example with Row:

Animate[Row[{Graphics[Point[AngleVector[t]], PlotRange -> 1.1, 
    Frame -> True], 
   Graphics[Point[AngleVector[2 t]], PlotRange -> 1.1, 
    Frame -> True]}], {t, 0, 2 Pi, Pi/100}]