Inertia - Pen In Bottle
To illustrate inertia of rest.
Cola bottle, 12" embroidery hoop, and Pilot pen,
Balancing this thing requires a good deal of practice and/or skill!!
The felt tip end of a Pilot pen is balanced on a 12" embroidery hoop, which in turn is balanced on a Coca-Cola bottle. Yanking the hoop out from under the pen by the leading side allows the pen to fall straight downward into the Cola bottle.
Martin Gardner, Physics Trick of the Month: Bottle, Hoop, and Dime TPT 32, 80 (1994).