1J20.45 - High Wire Cyclist (Ernie the Balancing Bear)
Show a stable system with the center of gravity outside of the body.
Connect the two weighted poles to Ernie. Place two bench rods with hooks at opposite ends of the lecture bench. Connect the hooks with the string in Ernie's box. Adjust one bench rod hook so that Ernie starts about four feet above the lecture bench. Adjust the other hook so that when released, Ernie travels the full length of the string without crashing into the low end. He should come to rest approximately two feet from the lower bench rod. (optional, provide putty for changing center of mass, explain to instructor how to use the putty)
Release Ernie from rest on the wire near the taller bench rod.
This demonstration can be run a second time with putty placed on one of the weighted poles. It changes the center of gravity of the system, but Ernie is still stable and able to travel the length of the wire because the center of mass is still below the wheel.
The cyclist remains stable because the balance pole keeps the center of gravity below the wire.