MECHANICS - NEWTON'S FIRST LAW - INERTIA OF REST NC State University Faculty Access

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Pen and Embroidery Hoop
# 1F20.36


Description: No matter the pen or bottle used, this demonstration of the inertia of rest requires practice and knowledge of the trick (not really a trick) to have this "in the bag" (or bottle...)

Instructions: Balance the hoop on the mouth of the bottle, and a pen (directly above the bottle) on the hoop. Ask the students what they think will happen when the hoop is removed, even have a student come up to prove it. They often will try to push the hoop off the bottle by approaching it from outside of the hoop. This will pop the pen up in the air, and it will most likely miss the target. The trick mentioned above is to approach the hoop from inside the hoop. When you grab the hoop from inside, the hoop compresses a bit, and the pen will have no initial upward motion.

Hazards: None.

Parts: Pop bottle (or flask)
Pen (or wire nut)
Embroidery hoop

Purchased/Built: built

Setup Time: 5 min

Quant. in Demo Room: 1


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