To apply the Differential strategy,
we need to trace out in detail the motion of the blue
coin as it rolls -- without slipping --
around the red.
This we have done in the adjacent diagram,
where we have shown where points on the top (blue) coin -- marked with a blob --
touch the lower (red) coin during the rolling.
When the blue coin has through half its circumference along half the circumference of the red coin,
then the top of blue coin is touching the bottom of the red coin, like so:
|Note that the top of the blue coin ends up touching the bottom of the red coin -- meaning that the blue coin rolls until finally|
The same Differential motivated approach is implicit
in the adjacent diagram::
which shows, point by point, which circumferential points are touching during the "real" rolling.
This figure is reproduced from the paper, Andrea di Sessa, "Phenomenology and the Evolution of Intuition". in Deidre Gentner and Albert L. Stevens, (Editors), Mental Models, Lawrence Erlbaum Assoc., Hillsdale N.J., pp 15-33 (1983).
|Process motivated solution to the Coin Problem|
|Reciprocity/Symmetry solution to the Coin Problem|
|Einstein's solution to the Coin Problem|
|Homepage for the Coin Problem|
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