MathLapse: Constructions by pin-and-string — conics
MathLapse Festival 2016 Winner. This MathLapse illustrates a process for drawing the three conics (ellipse, parabola and hyperbola) by pin-and-string constructions.
There is a string attached to two nails. The string is stretched using chalk; when the chalk slides along the string, an ellipse is drawn.
There is a string attached to a nail and to the top of a set-square that is resting on a ruler (not touching the nail). With the chalk the string is stretched and pushed against the set-square: when the set-square slides on the ruler, the chalk draws a parabola arc.
A string is attached to a nail and to one end of a ruler, the other end of which rotates around another nail. With the chalk the string is stretched and pushed against the ruler: when the ruler turns around the second nail, the chalk draws a hyperbola arc.