PURPOSE: To illustrate inertia of motion.

DESCRIPTION: A pencil is accelerated to almost the speed of sound by blasting it through a four-foot tube using a carbon dioxide fire extinguisher. The pencil will readily impale itself on a piece of 3/8" plywood. With a little bit of luck the pencil point will be virtually intact, although sometimes you need to re-sharpen it after the demonstration, as seen in the photograph at the right.

SUGGESTIONS: CAUTION: Be sure that the hose fitting is securely attached to the tube and that the plastic shield is in place before firing. This is potentially a dangerous demonstration.

REFERENCES: (PIRA 1F30.50)

EQUIPMENT: Cart with pencil blowgun tube and fire extinguisher with required fittings, sharpened No. 4 pencils, 4"x4" squares of 3/8" plywood, as photographed.

SETUP TIME: None.