# How can I animate two beads each sliding on its own frictionless rail? [closed]

I am told to animate two beads sliding on rails in Mathematica, but I am very confused on how to get a mass on a rail and it move up and down the rail.

## closed as off-topic by Daniel Lichtblau, m_goldberg, MarcoB, bbgodfrey, Carl LangeApr 24 at 21:26

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• Have you been able to model a single sliding bead yet? Any code to share? – MikeY Apr 20 at 11:43
• Is it 2D or 3D? – Alex Trounev Apr 20 at 19:19

If there are no restrictions on r, x, then the solution is

eq = {x''[t] == -k*(x[t] - r[t]*Cos[theta]),
r''[t] == -k*(r[t] - x[t]*Cos[theta])};

theta = Pi/4; k = 1;
ic = {x[0] == 1, r[0] == 0, x'[0] == 0, r'[0] == 0};
sol = NDSolve[{eq, ic}, {x, r}, {t, 0, 20}]

lst = Table[
Graphics[{{Line[{{-1, 0}, {1, 0}}],
Line[{{-Cos[theta], -Sin[theta]}, {Cos[theta],
Sin[theta]}}]}, {Green,
Line[{{x[t], 0}, {r[t]*Cos[theta], r[t]*Sin[theta]}} /.
sol]}, {Red, PointSize[.05],  Point[{x[t], 0} /. sol],
Point[{r[t]*Cos[theta], r[t]*Sin[theta]} /. sol]}}], {t, 0,
10, .1}];

ListAnimate[lst]