Blackboard Ellipse Maker

DCS Code: 1L20.50 Last Updated: March 27, 2026
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Purpose

Draws precise ellipses on the blackboard using a string-and-pulley mechanism that enforces the constant-distance-sum definition. Illustrates Kepler's First Law and shows how changing the focus separation changes eccentricity.

Blackboard with several concentric chalk ellipses of varying eccentricity; two magnetic pulleys serve as foci with a string loop running to a third chalk-holding pulley below
Figure 1: Several ellipses drawn with increasing focus separation. Two magnetic pulleys mark the foci; a string loop and chalk-holding pulley enforce the constant-distance-sum constraint.