# Animating two rotating circles

I have two circles:

dottedCircle1[{x_, y_}, angle_, rad_] := {Circle[{x, y}, rad],
Line[{{x, y}, rad {Sin[angle], Cos[angle]} + {x, y}}],
PointSize[0.03], RGBColor[1, 0, 0],
Point[rad {Sin[angle], Cos[angle]} + {x, y}]}

dottedCircle2[{x_, y_}, angle_, rad_] := {Circle[{x, y}, rad],
Line[{{x, y}, rad {Sin[angle], Cos[angle]} + {x, y}}],
PointSize[0.03], RGBColor[2, 2, 0],
Point[rad {Sin[angle], Cos[angle]} + {x, y}]}

Show[Graphics[dottedCircle1[{0, 0}, Pi, 1]], AspectRatio -> Automatic]


and I want them spinning with some specific speeds.

First one should rotating with constant speed f0 and the second one should starts to rotate by rubbing the first one (f1=f0 r/R (1-exp(t/T))).

Does anyone know at least how to make them show together (side by side) and spin?

• have you read the documentation of Dynamic? here – tsuresuregusa May 14 '16 at 21:22

## 1 Answer

Manipulate[Show[Graphics[dottedCircle1[{0, 0}, Pi/2 + a, R]],
Graphics[dottedCircle2[{R + r, 0}, -Pi/2 + s a, r]], AspectRatio -> Automatic],
{a, 0, 2 Pi}, {{R, 1}, 0, 10}, {{r, .5}, 0, 10}, {{s, 0}, 0, 10, 1}] 