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(See also live, Java versions of the following sketches, thanks to Monika Schwarze!)
Elevator Doors  Ken Koedinger
Move the Control Point left to open the doors.
Peaucellier's Linkage  Nick Jackiw
Fixed rods create the blue rhombus ABCD. Peaucellier's linkage is of especial interest in that it generates (by Point X) a line which is mathematically genuine (as opposed to the approximate lines generated by linkages such as the sewing machine). (In practice, PeaucellierŐs linkage contains too many jointed parts to be mechanically reliable.
Adapted from Mathematics Meets Technology,
by Brian Bolt (1991, Cambridge University Press)
Sewing Machine  Nick Jackiw
In the Sewing Machine, fixed bars AB and BC move as A is rotated on a flywheel. Brackets constrain the motion of BC into a straight line, resulting in the upanddown stroke of the needle at point C. Only the sewing machine's bracket constrains angular motion into an approximation of linear motion.
Adapted from Mathematics Meets Technology,
by Brian Bolt (1991, Cambridge University Press)
Windshield Wiper  Nick Jackiw
As the motor on the left rotates, a fixed rod connects A to an arbitrary point on the circumference of the follower. The windshield wiper is to an extension of the follower's radius through this point of attachment. Explore various wiping motions. Can you determine when the wiper will wipe the largest area? What must be true of the relation between the follower and the motor?
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